Date: 1966. Image Courtesy www.VintageCornets.com
This is a somewhat rare instrument in that Conn didn't usually make silver plated instruments anymore by 1966. The reason this is a silver plated instrument might be due to its serial number: K00001. Although it might not be immediately apparent from the picture, this instrument has a gold wash inside the bell. It is the non-Coprion version of the 9A, and the short model version of the 6A Long model Victor cornet. A 1966 catalog picture shows that the 5A has a nickel plated leadpipe, but not a nickel valve casing.
The 5A Victor has a #2 1/2 bore (0.485"). I strongly suspect it has top spring valves. Like other post-1960 (-ish) Connstellation and Victor models, it has a third slide stop screw. It was introduced sometime in 1961, and was produced until at least 1971. I suspect the appearance of the 5A might coincide with the end of production of the 6A Victor long model cornet.
Features include Lustre-Conn finish and for the 1961 and 1962 models Tri-C valves.
What Conn said in 1966:
Outstanding short model cornet for advanced student and professional. Balanced design. True cornet sound is well centered and highly responsive. Special left hand grip eliminates cramped position. 1-piece mouthpipe-mouthpiece receiver, third valve throw ring, micro-finish mouthpipe, 12 special braces. Length: 15". Bell: 4 3/4".