As far as I know and seen the s/n's of the 50th Anniversary models have a "50" in front following by the year (92 to 94) and a four digit number. 6541 items were made.
Maybe you could post some pictures of your camera here in the forum? Use the "Upload Image" function left of the message entry field in your answer. Thank you.
Separate 300 of 50 Year KMZ were made as first batch in 1992 with 92 prefix. The ones with 50 are the second additional batch. It concerns me that it's a 122K so it can't be 50 years and it's not 1997 model so it can't be Moscow 850, and it can't be 50 years victory model since that one is also plain 122 although it is from 1995... post pictures!