This is from Dig's chart that you linked

[Linked Image from photos.smugmug.com]

The Supplementary Nitro Proof Revision of 1904 is here from The Gun and Its Development, 1907
http://books.google.com/books?id=3HMCAAAAYAAJ&pg=PA280
p. 291 mentions the 1896 Rules "Maximum" mark, and p. 292 shows the MAXm. powder grains and shot mark. I don't know when that was discontinued and only the "oz. Shot mark" was stamped.

https://www.vintageguns.co.uk/magazine/rules-of-proof-5-london-

This is an 1896 Lancaster marked “E.C.” (No. 1) 42 grains = 3 Dram with MAXm. SHOT 1 1/8 oz.

[Linked Image from photos.smugmug.com]

A Tolley 1896-1904 1 1/4 oz MAXm but not the grains

[Linked Image from photos.smugmug.com]

1904-1925 London Proof - no oz. SHOT
https://www.vintageguns.co.uk/magazine/rules-of-proof-6-london-
1904-1925 Birmingham reproof - no oz. SHOT
https://www.vintageguns.co.uk/magazine/rules-of-proof-8-re-proof-