Saw an SP1 today ser.# in the 17000 range. No buttstock storage, Stock was shiny, its been 36 yrs. since I had an M16 in my hands. I do remember no storage and I think they used to paint the furniture, any knowlege? could this SP1 have an M16 stock. That serial# is from the early 70s I think. Any info would be appreciated as I may buy this.