Found a site which has the PRR letter font which was used on their Steam engines and elsewhere. If anyone needs for web pages or whatever. http://crew4.hyperisland.se/henrik_karlsson/type/clarendon.htm
CLOSE, BUT NO CIGAR! The closest typeface to PRR lettering is Craw Clarendon, not plain old Clarendon. PRR's letters were slightly more elongated than what is on the site you show. This subject has been extensively discussed on the PRR-talk site, and the conclusion is that the letters conform to PRR drawings of each letter and number made by the engineering department and do not actually conform to any type face.