The polished 10K rolled gold plated round case measures 40 mm lug tip to lug tip x 29 mm wide not including the mono-pusher chronograph crown x 15 mm inside lug / strap width.
The aged patina metallic finish dial has a combination of aged lume arabic numeral hour markings, as well as the Bulova signature, minute track and running sub-second dial printed in black.
The lumed syringe style hour and minute hands are finished in black. The center sweep chronograph second hand is finished in black as well.
The 17 jewel 10AH chronograph movement is stamped with the bowed top "T" and functions well. The snap-back 10K RGP case back is stamped Bulova 3124763.
1942 Bulova Stop-Watch. The seconds track for the large and small sweep seems to differ on the Medico and ad is dated 1947.
I inserted what I believe to be the correct ad for you. Stop-Watch Ad is dated 1942. We don't see many of these, that's a beauty!
EDIT - My bad, 1943 by S/N
In reply to Fantastic information by DanG1972
The difference between 1942 and 1943 can be a single day. It's not uncommon to see a year difference between a case and movement. Pre 1948 watches are generally dated by the first number of the serial number combined with the date code on the movement and case style. Your watch has a number starting with a 3, which would indicate either 1933 or 1943. That combined with movement symbol and case style dates the watch as a 1943.