Is my Tele Vue 3X Barlow missing something?

I'm hoping one of you more experienced observers can help me out. I bought a secondhand TV 3X Barlow, which has the lock-screw but not the brass compression ring other ones seem to have (see mine in photo). So is mine faulty or is it just an older model? I now have a 2.5X Powermate and would like to sell the 3X Barlow, but don't want to offer it for sale if it's missing something. It does seem to work fine. Thanks so very much for any words of wisdom!

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Originally Posted by Walter Michener

I'm hoping one of you more experienced observers can help me out. I bought a secondhand TV 3X Barlow, which has the lock-screw but not the brass compression ring other ones seem to have (see mine in photo). So is mine faulty or is it just an older model? I now have a 2.5X Powermate and would like to sell the 3X Barlow, but don't want to offer it for sale if it's missing something. It does seem to work fine. Thanks so very much for any words of wisdom!

I don't know if the 3x barlow is missing a compression ring or not but the lock-screw should work as intended with the possible downside that the set screw may leave a small mark on the eyepiece barrel whereas a brass compression ring will not. I personally wouldn't consider that to be a deal breaker but someone else might. In some cases, I could also see a brass compression ring providing a more uniform amount of pressure to keep the eyepiece centered in the barlow but, in most cases, I don't think that's going to happen. 

Thanks for this, and you're correct, the lock-screw alone works perfectly (and doesn't leave marks!). I'm just concerned that a future buyer might wonder why it doesn't look like the ones currently on sale new.