Proprietary information
Sterling Arms Corp of Gasport NY made the Model 283 Target 300 pistol in 1970-71. The 300L (light barrel) was made the same years.
50-160
50-150 or so
The Sterling, which has been out of production for approximately 30 years, was an inexpensive pistol. It's value is minimal, in the area of $50 for one in excellent/working condition.
I just bought a magazine for my Sterling Arms 285 Husky .22 LR pistol from Gunclip website. gun show, gun shop, want ads
Assuming you mean a Sterling mdl 287 PPL in cal. .380, these retailed new for about $90.
Try e-gunparts.com
try egunparts
Ask a gunsmith for help
Best left to a gunsmith
Best left to a gun smith