Why would they give it a model number different than the model numbers given to the keys and spanners issued to other guns? If you just peruse the excerpts I've already posted you can see that variance.
All the TMs and Handbooks for all the various British QF and BL guns had keys and spanners - including hydraulic buffer spanners, in their basis of issue lists, packing instructions, storage instructions, etc. But again, they all have different model numbers.
Having said that, I do believe there is likely an element and degree of commonality among hydraulic buffer spanners from different guns. Sizes might be different. Configurations might be a little different. But form, fit, function and general shape will probably be similar. Like the way the two different US Naval gun wrenches 3Bay posted look similar. Meaning, if we find a photo of one, even if it's not the same model number, for the 4.5-incher, I do believe it will likely be close enough. And I said so before right here....
I haven't found a TM or Handbook for a gun with a hydraulic buffer later than the 1929 4.5 incher. Hence, no illustrations of ANY hydraulic buffer spanner, even if it has a different number for a different gun.
But I'm no longer looking.