How do I identify the type of rack rails I have and what servers they fit

The government agency my company supports has inherited a set of 11 servers from the previous contractor.  There are a number of sliding rails in a large pile that I have to match up and then determine if they can be used with the servers we have.  The servers are a mix of Dell 2850, 2950, and 1950 servers.  Most of the rails have some engravings such as RH PEP 904 and PEP 46 03. The sliding end pieces show R-U1071. I know these are relatively old servers, but the were used for a dev/test environment for a complicated system that we need to stand it up as is.

(I tried to insert pictures but the image loader hung and did not load the images.)

Thanks,

Mike