Yellow gold plate case top loader dated L4. Diamonds in flat top triangular mounts at 12, 3, and 9. I went back and forth on this one between Launcelot "A" and Beau Brummell "L" as I haven't opened it. Up until this posting, the only apparent difference between the two was jewel count and perhaps diamond mount shape (flat vs. arched top). 17 for Launcelot and 21 for BB.
After pouring through the Linebooks and available ads, I found only Launcelot until 1955/56. It is listed in the 1955 - 1957 Linebook as "discontinued". From 1957 forward, it is gone from the Linebooks and BB "L" appears with an upgraded movement.
Launcelot is included in price lists until 1964, but based on the "discontinued" notation, I would say Bulova was selling off unsold examples only past 1956.
Even without confirming jewel count and basing solely on case date prior to ad, I am confident this is a Launcelot "A" and it's a match to the 1955 ad below.
Here they are side by side.
.jpg)
(Left) 1954 Launcelot "A" (subject watch) (Right) 1956 Beau Brummell "L" (per 1957 Linebook)