Hi Merrittw-

Like Darrin said…   Lots of stuff under some Winchester barrels…

“CMS” is the type of steel…  Chrome moly steel, a.k.a. Winchester Proof Steel, was adopted in 1932 and many early barrel were stamped with a three letter code denoting the source of the steel.  “CMS” is not strictly an acronym for “Chrome Moly Steel” (even though it is Chrome Moly Steel) but that’s a topic for another discussion…

“VP in oval” stands for “Violent Proof” (or “Veritas Proof”, as Darrin said).  This was a standard proof test performed on earlier Nickel Steel barrel blanks befor they were rifled and was apparently applied to some of the the Winchester Proof Steel (CMS) barrels in ’32 and ’33, but was soon dropped as the CMS barrels were strong enough to not need it.

“1906” is Winchester’s under barrel designation for the 30 GOV’T’06 cartridge.

“Triangle I” is a standard inspector stamp found on pre-war Winchester barrels, receivers, and other parts.

“33” is the year of barrel manufacture, applied when the barrel was chambered and before they were polished, exposed roll marks applied, and blued.

The “A” suffix on the serial number was applied due to a change to the extractor of the M54 action.  The “A” extractors were not interchangeable with the “pre-A” extractors, so the suffix was applied to tell the factory which part to provide should a replacement be needed.

Hope this helps!!!

Lou