Yes, the Proof House declared in 35' that 2" would be proved at the max. service pressure of 2 1/2" (and 2 5/8") guns = 3 Dr. Eq. with 1 1/8 oz. shot = 3 1/4 tons by LUP or about 9,800 psi by Burrard's conversion

I went through the thread trying to document the proof level by dates:
33' - 7/8 oz.
35' - One 7/8 oz. and two 1 oz.
36', 37', 38' - one each and all 7/8 oz.
38' - 1 1/8 oz.
46' - 7/8 oz.
50' - 1 1/8 oz.
54' - 1 1/8 oz.
56' - 1 1/8 oz.
and the undated Alex Martin S&W 1 1/8 oz.
It appears that the proof pressures were the same, but the service LOAD was marked differently.

1947 edition of Burrard's The Modern Shotgun lists a "Low Velocity: 2" load with 2.2 Dr. Eq. (24 grains of a 33 grain powder) and 1 oz. shot. No pressure was provided.
It is possible those 2" guns marked 1 oz. and 1 1/8 oz. were to use the lighter powder load?

This however from Henry Sharp, Shooting Times, 1939 back on p. 8 listing 2 loads for the 2", with the 1 oz. just introduced:
26 grains Curtis’s & Harvey “Diamond Smokeless” with 7/8 oz. shot = 2.36 Dr. Eq
28 grains "Empire" with 1 oz. shot = 2.55 Dr. Eq.

The "highest mean service pressure" for the 2 1/2” cartridge was lowered in 1954 to 3 tons - 8,960 psi and for the 2” cartridge to 2 3/4 tons = about 8,200 psi.
Standard service is about 75% of max. service

The 1955 edition of Burrard's lists standard load & pressures for 2" cartridges at 7/8 oz. 2.36 Dr. Eq. (26 grains of 33 grain = 3 Dr.Eq. powder) Service 2.25 tons = 6,440 psi; Max. Service 3.0 tons = 8,960 psi.

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