Looks like a relacquer, which might explain why there'a a mysterious "5" where there should be a "3." Notice how the "pat applied for" has been partly buffed away? Looks like the remaining original digits on the serial # have been heavily buffed too. Fortunately, the bell engraving came through the process OK. Maybe there was some pitting corrosion local to the serial # that the tech felt obligated to buff away, then incorrectly restored the first digit with a 5. It otherwise looks like a good relac job. The fact that it's a relacquer is a strike against its market value. Relacquers tend not to be trusted, because relacquering is often done after repairs of major damage, and the buffing can put post hinges outside of their tolerances and damage toneholes. Verify that there aren't excessive gaps between any of the posts and keyrods, or damage to the tonehole rims, as a result of buffing. Be prepared to answer that sort of question from buyers. Saxgourmet's online vintage saxophone value guide is a good place to start, then adjust for condition and the fact that this is a down market for vintage horns right now. Also check closing prices for comparable horns on eBay. It might be a great player's horn, just not a top dollar one.