Olds Military Model Trumpet
The Military Model trumpet was introduced by F.E. Olds and Son in about 1933 with the distinctive hammered finished bell as shown here. The first image to the left is taken from a catalog published in about 1937, which is when this trumpet was made. There are a few earlier Olds trumpets with hammered bells that appear to predate this introduction, but the Military was the only model where this was the standard finish.
Other makers copied this finish but only on instruments of much lower quality. Olds instruments were always superior in construction and playing qualities. Conventional wisdom is that the bore of a brass instrument must be as smooth as possible for maximum acoustical efficiency. In my experience, Olds trumpets and cornets with hammered bells are all excellent playing instruments (assuming that they haven't been modified or otherwise abused or worn out). In the manufacturing of these bells, the inside of the final flare is scraped and polished to remove the backside of the hammer dents, but these bumps are present in the rest of the bell interior.
The Military Model trumpets and cornets were also available by special order with smooth bells. I have come across a few of these and it is interesting to note that the bells are made of extremely thin brass, measuring about .015, the hammered variety being about .025". It certainly makes sense that a considerable amount of brass would need to be removed from the interior of the bell flares to make them smooth and this would probably be impossible with the thinner bell brass.
The unique bell engraving, with American bald eagle, seen here appears on every Military Model that I have seen whether with hammered finish or not. From their introduction the Military Models had mobile third valve slides and this has a stop rod to prevent it from falling out as well as a similar looking stop rod on the main tuning slide for quick change to A. The valve section is marked "M" (medium) and is the smaller of three sizes made by Olds, with a bore size of .453", a narrow bell flare and the rim diameter is only 4 1/16".
The curves are narrow, making this trumpet longer than most at 20 1/4" with the mouthpiece removed (19 3/8" from bell rim to curve). It is a very responsive playing instrument with excellent intonation and a very brilliant sound, especially when played loudly. In contrast, my French Model Olds trumpet with hammered bell and larger proportions throughout has a very warm timbre.
The trumpet pictured appears to be extremely well preserved, while in fact it required some restoration and replacement of parts supplied from a parts horn.