The SML Rev. B
The next revision of the SML horns came around s/n 45xx, when the bell keys were switched to the right side of the horn (as you're playing) -- a technical innovation that tenor and bari sax players applaud. Other features appeared to be the same as Rev A horns, but it's distinctly possible that there were more modifications to bore size, etc. Note also the subtle differences in keywork on the horns pictured here (esp. the chromatic F#) and that the engraving is significantly more elaborate than the Rev. A horns.
(Stupid SML trivia note: by 1947, the 6-pointed star[s] on the bell became 5-pointed.)
Other model names:
(quote from ad) s/n: 5117 "Super Luxe" alto
Rolled tone-holes, 95% original satin silver plate, the bell with Art Deco engraving and "SML Super Luxe" engraving in addition to the normal SML logo and address. Rib construction for the stacks, chromatic F# and palm keys, rolled tone-holes but no adjusting screws to the stacks. G#/C#/B/Bb cluster curved like the later "Gold Medal" instruments. Neck has normal SML strut under it. Pearl key touches for LH 8va. key. Additional keywork for high C to D trill, RH G# trill and 1 & 3 forked Eb for the right hand. Low B & Bb pad cups are away from the player. Rare alto incorporating some of the features of the later "Gold Medal" sax.1
For further notes on SML model names, please see my comments on the Rev A horns.