The model 500 embodied the style of its era, particularly when set in the "Copenhagen" desk-style cabinet:
This cabinet is described in a Singer brochure as "a modern dual-purpose desk of the finest hardwood and veneers with handsome brash finished pulls and ferrules. Comes in blonde or walnut finish." This one, obviously, is blonde.
The "new" Slant-O-Matic model 500 improved on its predecessor, the 401, with its space-age styling and the addition of a micro-stitch length control, concealed spool pins and bobbin winder, and a numbered pressure dial. Otherwise, it's a 401. Both machines are fabulous stitchers!
The 500 would have come with a manual, of course, plus an accessory case. A buttonholer was a common option; the pink "Jetson's" case complements the style of the machine.
The 500 and the 401 have built-in camstacks, selected using the two dials on front. Those dials, plus the needle-position and stitch-length levers, plus the double-needle capability can all be used in a mix-and-match fashion to produce a zillion decorative stitches. Or you can use any of the "top hat" style cams for even more stitches.
One nice feature of this machine is that you can load two regular needles into the needleclamp to do double-needle stitching, rather than having to purchase a special twin-needle.