Venom tunes start from 1983 to 2005. Serial number give an indication when produced and slight indication of year of tune. If it's a lazaglide it will have a sticker to say so up till around 1999 when the twin Cobra sticker replaced both stickers. Without seeing the rifle it's hard to give a true valuation. 177 fetches a little more than .22 as the calibre in vogue. Mach 1.5