Question from history student

I have a question regarding architectural plans which I hope this group can help me with?
I am a history student at Murdoch Uni, West Australia, and I am currently researching a building - the former Water Police Station and Quarters, Marine Terrace, Fremantle. Different authors credit the architectural design to either John Grainger (chief govt architect- Public Works Dept. at the time, 1903 - suffering ill-health) or Hillson Beasley (assistant-2IC). Both men were very talented and designed some significant West Australian public buildings. Hoping to solve this (with my limited architectural knowledge), earlier today I viewed the plans of the building at the State Records Office. They were not signed or attributed obviously to anyone, however, there was a mark-monogram in the lower left corner that appears as 'HB'. Do, or did government architects leave cryptic clues of their identity on their plans? I have tried, but cannot enclose a photograph of the mark, (can email it later?) - 03 is the year, but I do not understand - Exd (executed by?): or the artistic Ws?
I am not suitably educated to compare styles of buildings designed by the two ...they all look lovely to me!
Anyway, I hope someone can enlighten me! The building is very impressive, 'Federation Free Classical style' and I think it is important that credit for the design is given to the right person (albeit posthumously) ...I am leaning towards Beasley, although 'authoritative' records credit Grainger?
Regards, Pat
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