I own G&H # 435, only two numbers off from this rifle on Gunbroker.
It too is marked 30/25 M1. Mine is a 20" barreled short rifle in 30-06, with a fixed ghost ring rear sight. I bought it cheap because nobody could figure out what it really was.
What my rifle is (was) is an NRA Sporter, with it's original USGI Sporter barrel (the original star gauge marks are still on the underside of the barrel), it still has the rounded front edge on the receiver, but the barrel has had the last 4" cut off (the SA ordnance bomb and dates are gone). The original serial number had been restamped on the bottom of the receiver, and as I recall, it dates from late 1925. At one time, I had quite a long conversation with Paul Chapman of G&H, and was surprised to learn that most of the 30-06 barrels of this era that G&H used were of USGI origin. That makes sense because star gauged barrels, both National Match and Sporter were easily, and relatively cheaply, available from the DCM, and were known to be of a high quality.
In keeping with English double rifles of the period, and because of a fixed rear sight, G&H placed the cartridge load on the barrel. In October 1925, the US Military introduced the 30-06 M1 loading. The original USGI loading of the 30-06 was the M1906, with a 150 grain flat based cupronickle bullet. The M1 load was a 173 grain boattail bullet, and had a much flatter, and longer, trajectory. Because of the flatter trajectory, and the increased danger space, the M1 loading was discontinued, and the M2 loading was introduced in 1940. The M1 boattail bullet was retained for match grade ammunition, essentially becoming the M72 bullet used in both the 30-06 and 7.62 NATO M72 and M118 ammunition of the 1950s, 60s and 70s.
There has been /is much speculation of the 30/25 M1 nomenclature, but I submit that instead of the original load being 30/06 (meaning 30 caliber, model 1906) G&H placed the new loading information , 30 caliber/ 1925 variation, M1 loading to distinguish these rifles. This is only the second rifle I have seen so marked, it will be a 30-06, chambered for the M1 loading. Having a fixed rear sight, my rifle needed that load information on the barrel, as it would have been "regulated" with that load, and any other load might not shoot to the sights. The Gunbroker rifle, with a Lyman 48, really doesn't need the 30/25 M1 notation, but I wonder if # 436 has it too............
Lastly, as to the stock on this rifle, I can't really say what it is, but I can unequivocally say what it isn't! That stock in no way lives up to Griffin and Howe's standards..............
HTH
By the way, and I haven't gone back and looked at the Gunbroker rifle yet, and I don't want to change or loose my entire post, but with a last glance, my rifle is actually marked 30/25 M.1, not 30/25 M1
