Don't believe it is a F. Pratt frame. He would have put his own transfers back on it, rather than renovated by... Pratt's was quite a well known shop and it would fair to assume your frame was a decent lightweight to have been refinished. The top eyes on the seat stays and the rear dropout with the downward tang (For use with Osgear) all indicate a build date of late 1940s, very early 1950s. A decent photograph of the lugs (seat and head) and frame number would be helpful in trying to tie down the builder. Your frame may be a Claud at a guess as Frederick Pratt built frames with Claud Butler before he went out on his own and it may have been one he actually built at C.B. But like I said, need more information.