The first Kay bass manufactured (1937) was apparently the Concert or the (C-1). The concert bass had rounded shoulders or bouts, which made the bass easier to play while sitting. The Maestro model (M-1), having the violin shape, where the middle ribs form a point at their junction with both the upper and lower ribs was manufactured after Kay was well into production.
A blonde finish was optional and (M-1) Kay basses with a blonde finish came to be known as the (M-4) models. M-4 models carried inletted purfling and an ebony fingerboard. These lasted through 1940 then (M-4) was renamed the (M-1-B), of course the B being for blonde finish.
The M-1-B did not have inletted purfling.""