Same story as the 503A. The 500 model series of sewing machines affectionately called the “Rocketeer”. This name was given to it by collectors, not Singer. It is known for its futuristic retro styling inspired by the times it was born into… namely the “space age”. They were manufactured between 1961 and 1963 in Singer’s Anderson manufacturing plant. The 500 series has become iconic in the Singer lineup and is still a very desirable machine to own.
Aside from its futuristic styling, the 50A is mechanically identical to the 401A. Only minor changes such as the location of the bobbin winder, spring loaded folding spool pins under the top cover, and a presser foot pressure dial distinguish the two.
More to add… it’s a work in progress so check back later!