Russian Optics

Russian night vision scope IPN58 as used on Kalasnikov, SVD, FPK and others. I would like to have a little idea as to what these are worth, I have chance to buy one for $1000 and am wondering if this is a fair price---I have no clue, so would appreciate any comments. I'm interested in it as a collecter item and I have a FPK and RPK to use it on.Thanks