Papermaker,
A 4803 is a Clausing, not an Atlas, regardless of what's on the nameplate. Atlas bought Clausing and then later changed the company name from Atlas to Clausing for reasons having nothing to do with the machines that turn up on H-M. In the period between the purchase (around 1950) and the name change (early 60's) all of the Clausing model numbers were changed. But AFAIK, the two lines never shared parts. For help, advice, discussion about yours, you'd probably be better served if you move over to the Clausing forum. I can move this thread over there for you or you can just start a new thread.
Robert D.