Just happened to run across the same kind of acetate label on Discogs. This version features a bit of a radio show, the Charlie McCarthy Show with Fats Waller, recorded and broadcast on NBC on December 5, 1943, 10 days before Waller died of pneumonia.
These acetates just happen to be in my collection of some 45,000 78s. I had no idea who the artists are before reading the notes on this page. They certainly are interesting, as Sanders Terry is Sonny Terry & McKinley Morganfield is Muddy Waters.
There is a real chance the 3 acetates uploaded were originally issued along with the normal shellac 78s at the time or as demo copies before shellac of these when into production. I haven't seen any others acetates by the Library of Congress but just found a few more from Audio Devices, Inc., New York by Kid Ory & New Orleans Bootblacks. These also came in sleeves with regularly issued swing/Jazz 78s from the early 1940's.
I still wonder about the nature of your acetate disc. It doesn't look like a private home recording. It it was one, it probably wouldn't have the legal notice "Public performance prohibited without license." The stroboscope ring around it ("Appears stationary under 50 ∼ lamp") seems unusual too. Could this have been produced by the Library of Congress itself? It is still possible to request copies of Library of Congress audio material (https://www.loc.gov/folklife/recordering.html), and someone may have ordered one back in the late 1930s.
The numbers on the acetates, 19A and 19B, are the numbers assigned to these songs in the Library Of Congress series The Archive Of American Folk Song AAFS 19. Originally, they seem to have been released in 1942 as part of a 5-record shellac album, Album IV "Afro-American Blues And Game Songs" (source, pages 10-11).
The original AAFS 19 labels list the A side matrix number as LC 3, the B side matrix number as LC 56.
In 1976, they were re-issued on the Library of Congress LP "Afro-American Blues And Game Songs" (AAFS L4).
These acetates are Library of Congress recordings. The dates on them are the year they were recorded. It's not easy to say when they were pressed and used for dubbing.