I've seen recent POF-5 pistols with 17 year of manufacture with a C-prefix. What's common between all POF SerNos is the fact they only use a maximum of five numbers after the letter, so would assume a maximum production run of 99,999 before they start over at 00001 with next subsequent letter. I tried to find some history of when POF first started manufacturing their MP5s to see if the first picture above could possibly be a first year issue (if they had the capacity to crank out 8000 per year back then), but there's not much info on the web. I have some pics of their G3s burried somewhere too, but can't recall if I got any up close pics of those guns, but will surely post when I locate them...