[RR84]

Is anybody here familiar with the different revisions of the MX? I just received my 2nd MX (914***) and noticed some slight variations from my original (418***). Here's what I noticed:

1. The 'MX' logo on the front face of the camera is bolder on the later model, and finer on the earlier
2. The design of the memo holder on the rear of the camera is square on the later model, and rectangular on the earlier
3. The later model has 'Asahi Opt. Co. Japan' embossed on the rear upper body of the camera, while the earlier model has it located on the film memo holder.
4. The text inside the viewfinder representing the shutter speed dial is bolder on the earlier model, and finer on the later
5. The aperture window above the lens mount seem to differ slightly
6. The shutter 'cocked' indicator is slightly larger on the later model than the earlier
7. The later model seems to be a fraction lighter than the earlier, but I'm yet to confirm

Feel free to add any further variations you have noticed between revisions.

[tlong423]

Is anybody here familiar with the different revisions of the MX? I just received my 2nd MX (914***) and noticed some slight variations from my original (418***). Here's what I noticed:

1. The 'MX' logo on the front face of the camera is bolder on the later model, and finer on the earlier
2. The design of the memo holder on the rear of the camera is square on the later model, and rectangular on the earlier
3. The later model has 'Asahi Opt. Co. Japan' embossed on the rear upper body of the camera, while the earlier model has it located on the film memo holder.
4. The text inside the viewfinder representing the shutter speed dial is bolder on the earlier model, and finer on the later
5. The aperture window above the lens mount seem to differ slightly
6. The shutter 'cocked' indicator is slightly larger on the later model than the earlier
7. The later model seems to be a fraction lighter than the earlier, but I'm yet to confirm

Feel free to add any further variations you have noticed between revisions.

I can remember buying my first MX body in the spring of 1978 -- it had the black-painted metal film tab holder on the back. By the time I bought my second MX body in the spring of 1985, they had switched to a plastic film tab holder with (as you've described) the "Asahi Opt. Co. Japan" on the the base of the tab holder. Other than that, I had never noticed any of the other subtle things you've listed. I've owned at least five other MX bodies in my life, and they have each fallen into one of the two "versions" I've mentioned (i.e., with regard to the film tab holder).

[RR84]

For anyone wanting to know the differences between the two revisions, check out this site (Japanese text). Basically, the most noticeable differences are:

- Serials beginning with 9 are the early revision which have the square, metal rear film holder and 'Asahi Opt. Co. Japan' embossed on the rear upper body of the camera.
- Serials beginning with 4 are the late revision which have a plastic, rectangular rear film holder.

I have one of each. Personally, I prefer the later model (418***).

[sandbasser]

I too have both 4*** & 9*** MX bodies; but, both have the plastic rectangular rear film box holder and neither has the "Asahi Opt. Co. Japan" embossed below the wind lever.

Both are good shooters, both 'sound' about the same, while the 'newer' numbered one has a smoother feeling wind action; but, both are obviously very, very used.

Very odd.

(I am not the original owner of either body so I can not attest to their provenance. But, I wouldn't be surprised if sometime during their lives bases or backs were interchanged.)

And, wouldn't it be nice if Pentax's Serial Numbers made sense.

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Last edited by sandbasser; 03-11-2016 at 06:31 AM. Reason: minor additions

[wombat2go]

serial 9363534, a black mx has a steel memo, of inside dimensions 26 mm H by 30 mm W
No Asahi name on rear.
The hub of the wind arm has a sharply defined bevel, and not rounded like RR84's photos.

[arnold]

I have four 900 series, 92299354 to 9389744 and one 4096519. The only difference I can see is the 400 series doesn't have the embossing below the winder. All have a (edit square) metal film holder. The 400 has a softer wind than some of the 900s but not all.

[TomB_tx]

A non-visible revision is inside the baseplate. The shutter curtain tensions are set by small worm gears. I had picked up one MX with bad shutter capping (speed of opening curtain slower than closing curtain, so part of the frame is unexposed), and sent it to Eric for service. When I got it back the capping was worse, so I investigated. That MX used plastic in the worm gear assembly, which had deformed and let the gears "jump" - losing tension after Eric had adjusted them.
The othe MXs I have all have metal worm gears.

[RR84]

A non-visible revision is inside the baseplate. The shutter curtain tensions are set by small worm gears. I had picked up one MX with bad shutter capping (speed of opening curtain slower than closing curtain, so part of the frame is unexposed), and sent it to Eric for service. When I got it back the capping was worse, so I investigated. That MX used plastic in the worm gear assembly, which had deformed and let the gears "jump" - losing tension after Eric had adjusted them.
The othe MXs I have all have metal worm gears.

Interesting.. What serial number range was that MX?

[sandbasser]

A non-visible revision is inside the baseplate. The shutter curtain tensions are set by small worm gears. I had picked up one MX with bad shutter capping (speed of opening curtain slower than closing curtain, so part of the frame is unexposed), and sent it to Eric for service. When I got it back the capping was worse, so I investigated. That MX used plastic in the worm gear assembly, which had deformed and let the gears "jump" - losing tension after Eric had adjusted them.
The othe MXs I have all have metal worm gears.

TomB-tx - Good catch... I just pulled the base plates from my 4* and 9* MXs. There are definitely what appears to be plastic worm gears on the 9* - and metal on the 4*. I just got the 9* back from Eric it 'seems' OK but I'm waiting for film development...should be ready the 14th or 15th, then I'll know. (The 4* is a recent acquisition and I'm going to send it to Eric soon.) I tried taking some digital images but can't get close enough for clear views...must get Macro

[arnold]

How odd that gear problem didn't show up when being repaired. Plastic can deteriorate badly, especially in Australia under strong UV light. I have not checked to see if mine are plastic, but they are still working fine forty years on.

[Eyewanders]

I've noted difference is the two I have, but haven't ever completely taken stock.
I've an older black one is 9335591 and a newer silver that is 4492485.
The newer silver one doesn't have the "Asahi Opt Co., Japan" stamp anywhere that I've seen. The film card holder is plastic as mentioned before. It's slightly lighter overall. It also has a small rubber "grip" bit on the shutter lock switch as opposed to the all-metal "toothed" grip that the older one has. Those are the only differences I've noted.

[sandbasser]

I've noted difference is the two I have, but haven't ever completely taken stock.
I've an older black one is 9335591 and a newer silver that is 4492485.
The newer silver one doesn't have the "Asahi Opt Co., Japan" stamp anywhere that I've seen. The film card holder is plastic as mentioned before. It's slightly lighter overall. It also has a small rubber "grip" bit on the shutter lock switch as opposed to the all-metal "toothed" grip that the older one has. Those are the only differences I've noted.

#chickentender...Great catch! Both my 4* & 9* MXs have the small rubber "grip" on the shutter lock. To me that's further evidence that at some time (unknown to me) in the past my 'old' MX got some parts switched from a newer one, or maybe the older base with the serial number got moved to a newer body. I can't think of many reasons to do something like that. (This thread is really interesting!)

[ChrisPlatt]

Eric Hendrickson replaced the missing rubber "tooth" on the shutter release lock collar of one of my MX bodies.
IIRC he told me this part often falls off; it's only friction fit. Fortunately it's not real difficult to operate without it.

Chris

[TomB_tx]

OK, I've re-checked the gears that adjust the shutter curtain tension on my MX examples. Since the serial numbers are on the bottom plate, which can be swapped, and the film box frame is on the back, which is removable and could be swapped, I'm not sure what conclusions to draw.
The "white" plastic gears are on my example serial 4390xxx, which also has the plastic film frame on the back. The gears look like this:

I have three in the 918xxxx to 932xxxx serial range, and all these have the metal film frame, and gears that look like this:

And finally my black MX has serial 9479xxx has a plastic film frame, and gears like this:

The darker gears of the middle three look like steel or maybe heat treated brass. The "brass" gears on the last are...brass.
Often on high volume production items there are many running changes in internal parts that are not specified, if deemed interchangeable. That may be the case here.

[womble]

Don't forget the whole back is dead easy to remove in order to fit a databack or a bulk film back so the film holders might not be all that diagnostic.

K.