Dear Pentaxiani,
as written in my introduction I decided I have to have a K1000 because...well everybody has one.
I tried to gather as much information as possible on the different variants of the camera that lasted for 20 years, and I must confess that the database of this forum has been very useful BUT I still don't understand: it seems that there have been at least four different K1000, the Made in Japan, the Made in Hong Kong (the majority), the made in Taiwan and finally the made in China.
So if I understood correctly you can distinguish by the following characteristics:
1)MIJ: 55mm f2.0 lens, serial number on the left shoulder plus bump,Asahi Opt.Co.
Japan on the back
2)Made in HK: main variant, serial number on the button plate, 50mm F2.0 standard (first K then M), usually sticker with written "assembled in HK".
3)Made in Taiwan: screw on the left shoulder where Mark I has the bump, otherwise identical to Mark II, I've never seen a sticker "assembled in Taiwan".
4)Made in China : easy to spot because lighter and with top and button plate made of plastic, plus no Asahi logo.
And if I understood correctly at least for the first years of production we have to add a 1 to the first two digits of the serial number to get the year of manufacture, so:
75XXXXX-1976
76XXXXX-1977
77XXXXX-1978
78XXXXX-1979
The production from Japan to HK has been moved about 1978,so theoreticaly speaking if I want a 1978 MIJ K1000 I should look for a 78XXXXX camera Asahi Opt.Co.Japan.
Now, here my perplexities start because on ebay I found a lot of camera that corrisponded to the Mark I (serial number on the top, bump, 55 mm f2.0) BUT without the Japan engrave after the Asahi.Opt.Co....I mean really many! It can't be an error...so I wonder if these cameras are made in HK or in Japan...I've seen some of them with the 75 or 76 number so still in the MIJ production years range, in one case the camera had a sticker that stated "assembled in HK!"
The second question regards the Taiwan version: are we positive that any camera with the screw on the left should is MIROC? They are relatively common, but none had a sticker "assembled in Hong Kong", in short it looks like a mess to me!
The general consensus seems that the 55 f2.0 is better than the 50 mm cousin, but I was wondering if these lenses were also used outside Japan, anybody has an idea on the matter?