With the warning that uniforms aren't my area of expertise, I'm going to suggest it might be a Royal Horse Artillery uniform. Any takers? Any advance?
best - Garen
Edit: Just found this on our own forum:
viewtopic.php?f=19&t=2316Edit 2: Find My Past has a service record for a George Shearer, b. Bootle 1863, attested 1884 in the Royal Artillery - transferred to RHA Mar 1885

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Edit 3: Sorry - just seen this has been answered more comprehensively by Frogsmile, here:
viewtopic.php?f=19&t=6223&p=24872#p24872Though I can at least add that that does seem to be his service record at FMP.