Looks like a RCA CTC-4 (1955) with the Sylvania name on it... bet that is a 21AXP22 under that plastic insulator cone. Several brands were produced that were simply re-badged RCA CTC-4s... at one time, I had one that was branded Hallicrafters, but it really was identical to my RCA set.
ETF has pictures of the clones:
http://www.earlytelevision.org/rca_ctc_clone.html
jr