Your gun was produced in 1981 according to the serial number. The 99C's had the fat forearm for a few years starting in 1981, it was carried over from the 99CD which was produced from 1975 to 1980. I attached a photo of the front of my book which has a 99C like yours on the cover. If you really want to get addicted to 99's buy my book or Doug Murrays. There is a link below to get my info. David