I'm not a collector of wrenches, but have a couple of dozen, including a handful of this type - very few show any maker's marks at all.
In Sheffield, and also in Birmingham, in the UK manufacturers often made tools for each other, so they did not always stamp the tools they made at all. Also it was common to stamp a retailer's, or even an ironmongery shop's, name stamp on tools - which makes it very confusing when trying to identify a maker..
Owners' stamps, except in the case of large companies (e.g. rail, Post Office, WD) are rarely of the type of long engraved stamp (except on wooden parts of wood working tools) - so it was most likely stamped at source. i.e. by the maker...
A quick search for Warren + Wrench - finds an Australian manufacture, Warren & Brown, makers of automotive tools - possibly a line worth following up... Their web site states they have been in existence for 90 years, so back in the 1920's these wrenches were probably still being made, especially in country that relied heavily on agriculture and agricultural machinery...