I bought several items from someone on Astromart last year that I hope to use to make into a scope optimized for astrophotography. I want to get a larger secondary for this purpose. The primary mirror cell I got as part of the package is marked Novak, and the secondary holder looks just like the photo of a Novak holder I googled.
Anyway, the secondary is about three quarters of an inch thick with beveled edges, and the coating looks good to me. But I am not an expert: there is what looks to be a small water spot (1 mm?) and a couple of just visible sleeks. If it was big enough, I'd certainly use it. I do not know what type of glass it is, nor just how flat and smooth it is. Sorry!
I want to trade for a decent 3.1" secondary, preferably in a holder I can use with the spider for the holder I'm trading. But I might be able to make my own holder.
I am, of course, ready to add some cash to the deal. Or, I may have some accessory to add to the trade (for example, an Antares right angle, 8 x 50 erect image finder. The tube is pretty scratched up, but it's fully functional, and comes in a one-piece spring loaded holder that fits Synta and other scopes.)
(The photo below is of a Novak holder I googled, NOT the one I'm looking to trade -- I don't have a digital camera yet -- but it looks just like mine, except mine has a secondary in it!)