Grado SR100 with red lettering - value

Greetings. I have a pair of Grado SR-100s with red lettering that I bought new when they were first sold by Joe Grado. I've always loved the sound, but now find I only use them a few times each year. Having reached senior status and being in the midst of downsizing, etc. I want to sell them to someone who would appreciate them. They are in very good condition (except ear pads). I have searched the 'net but cannot find any pricing information. Can anyone help? Thanks.