Came across a working constellation gralflex slide projector model 500A and was wondering if it is worth anything and where to sell it.

Thanks

Doing the following searches shows that there is information about these available and maybe some that are for sale. You might want to contact persons on some of the links that you will find about selling it where the same or similar items are being sold.

Constellation Graflex Slide Projector Model 500A - Google Search

Constellation Graflex Slide Projector Model 500A - Google Image Search

Pacific Rim Camera:catalogt