Wow, all this variations.. didn't know that.
K1000 series number is 7358902, other than that, how do you know if it's made in japan vs china?
Wide angle: SMC Pentax 1:3.5/35
telelens: smc pentax-m 1:3.5 135mm
standardlens: smc pentax-m 1:2 50mm
macrolens: smc pentax-a 1:2.8 50mm
There are at least three main series, made in Japan, made in Hong Kong and made in Mainland China.
The MIJ were built with the other K series, the top plate is the same as the KX, the serial number is on it instead of the base plate and originally came with the K55 mm f2, they are relatively rare because in 1976-1978 it had to compete with the better spec's KM and KX:
Made in Hong Kong is the most abundant, it originally came with a M 50mm f2 or an A 50mm f2 according to the time it was produced:
A lot of people consider this camera made in Japan but it's not.
The made in China has plastic plates, no "Asahi" engraving and it's 100 gr. lighter than the original camera: