The value, as with most things, is in the rarity, completeness, and condition. Old Erector sets are pretty common. Yours seems to have a lot of the parts, and if the motors work it's a plus. But the condition of the case is pretty bad. I would estimate $50 on a good day. Yours would be a nice piece for someone wanting to complete a set who might be missing some of the pieces. Still a really cool toy! I love old and antique toys! A blast from the past, for sure!