I just dug out my unit to see abut the throat plate cover. I bought it to use with my 626 not even thinking about the plate cover! Fortunately, I have two--507661, 161825. I think that this should work on the 626 I bought it for and also the 403 I have in Sun City. I'll leave it here instead of taking it to SC but still haven't tried it on either machine even, tho I've had the unit for about 3 or 4 years now. Got it off Ebay and it has all the letters plus these 2 machine plates. There is a newer one that does larger letters but I have not been successful bidding on them. They usually don't have all the letters either. Of course, I'd have to investigate if they would work on my machines now that I realized the throat plate type is important.