if it's antique, pre 1950s, you can ask from 50 bucks upwards. Recent equipment, like from the 1980s is worth only less, unless it's from a great company, or has special built.
It depends on the model and how old it is. The thing about collectibles is that there are several variables; the difference between one model and another (same company and year) can be huge depending on how many were made and how many remain.
