[pentaxk10duser]

what does the M stand for if I see that on the lens will it fit and work on my K10d ty Steve

[Adam]

Yes it will work, with manual focus and manual metering control. No adapter is required.

here is how you would meter with the lens: https://www.pentaxforums.com/forums/pentax-dslr-discussion/130310-sv-m42-pentax-k-x.html

[Ash]

Yes, it will fit straight on, but you will have to implement the stop-down metering function of the K10D (see the tutorial on using M lenses on Pentax dSLRs) before you can shoot with the lens at your desired aperture setting.

[Stone G.]

what does the M stand for if I see that on the lens will it fit and work on my K10d ty Steve

The first Pentax lenses with K-boynet mount were simply labelled SMC Pentax. (Nowadays, we tend to call them Pentax-K, but the "K" is printed nowhere)

Next generation was labelled SMC Pentax-M (the ones you are asking for). In functionality they don't differ from the early SMC Pentax lenses.

Third generation was SMC Pentax-A, featuring automatic exposure control - provided that you have a proper camera body.

You can safely use them all on your K10D, as you can on any digital or analogue camera with a Pentax-K bayonet mount.

Interesting question, though........

.....anybody who would know: What DOES the "M" stand for???

[m42man]

Interesting question, though........

.....anybody who would know: What DOES the "M" stand for???

I rather doubt it stands for anything (what does "K" stand for?). It's surely just a model range identifier brought in to differentiate the new range from the previous (K).

So we go from K1000 etc. plus SMC lenses to MX, ME and SMC-M lenses. I think the new range was in response to Olympus, who were producing compact SLRs at that time (OM10, OM1, OM2). That's why the M lenses tend to be more compact (and therefore completely new, optically).