i place the sword as being made in 41-42 and as you mentioned it would be mid-war.
Popular belief has it that the brass tsubas were made prior to the steel ones, however, there is no real evidence to support this. Both brass and steel tsuba swords were made concurrently throughout the war until the wooden handle variants were introduced, with the brass ones being the initial types as we know.
The brass tsubas continued to be used up to the 160k range.
The steel tsubas are issued as low as 18k ranges and continued to the end of the war.
Also they were not confined to a particular sub-contractor/Arsenal, as both variants appear in the same number ranges from each of the sub-contractors.
As the 11mm brass tsubas were primarily used on the copper handled swords and a very few Aluminium variants,
with the available evidence, i would tend to agree that Suya is the only sub-contractor to have made them, although i have no definitive proof.
From the 10k range onwards we see the introduction of other sub-contractors such as Gifu and Iijima, none to my knowledge have had the 11mm tsuba.
I think our timelines are fairly consistent and similar, but our understanding of the events that occurred, differ.
I've been looking at the type 95 for a while now and this is what i have found from first hand observations.