There are 3 options,,call Remington and ask, they do not have it posted on there web site but might have it around.
Buy it---http://www.gungarage.com/remingtonacc.htm
Go to a gun dealer and ask, most have one for repair parts.
Contact Remington or try e-gunparts.com
Read the manual on: http://www.remington.com/products/firearms/rimfire/model-552/model-552-bdl-speedmaster.aspx
it is a model which is schematic
NUMRICH GUN PARTS SELLS THEM ON THEIR WEB SITE
let someone else do it.
No it's a centerfire, .35 remington.
Is it a Model 4 or a Model 6 or a rolling block? Try posting over at http://www.remingtonsociety.com/forums/
Remington's web site has a model history section. Ammunition hard to find so value not that great. Maybe 100 or so USD
Which version... the centerfire model or the .22 rimfire model? There is no serial number on the rimfire model 55. It was made prior to the requirement in 1968.
You first have to identify which model and then you need a good description of it's condition. A guess would be a model 4. Try the Remington firearms model history page and look at the model 4 or the later model 6 they have photo's they don't however have anything on the earlier models.
You can locate a schematic at http://www.remington.com/pdfs/om/om_11001187.pdf.
Go to www.e-gunparts.com/model.asp?idDept=204 very good diagram