The back on my crown has light traps on top and bottom but none on the right where the holder slides in though there is a groove. Should it have felt/velour in that groove?

Let's see . . . Pry open (carefully!) the gg right side as though to insert a holder. Hmmmm.

Yup. A crushed strip of fuzzy (50 years ago) felt on top and bottom (the long way). No light trap necessary on the left side. (light never moves to the left). I see now . . . No light trap on the right side either. Hmmmm (again). O. I. C. (that means Oh, I see) The ridge on the film holder mates up to the groove you see on the back on the back.

Amazing those 20th century engineers.

All seriousness aside. It's OK as is.

-Steve ;*)