Probably mid-70's. I carried them in my gun shop during the 1974-1978 period or so. S&W also was marketing pellet pistols in both .177 and .22 caliber back then, and the pellets were part of the product line. IIRC, S&W discontinued the pellet pistols and pellets around 1978-80 or so. Man, I haven't even thought about S&W pellets (or S&W pellet guns) for years. I wonder if I still have some from the left-over inventory from that time period - I'll have to look.