Yep, what Bryan said. There were two lens options - the Achromat and the Rapid Rectilinear. You have the former; that front piece is a hood/thread protector/let's make this look less cheap part. They weren't about to mill two separate shutter housings just to facilitate lens options.
I wouldn't worry much about it, though - I have the "better" lens option, and as I said, it's really only sharp at f/32, and barely acceptable for general work at f/16. Might be good for portraits, though.