Some years ago I also pulled out a No. 4 Trials sniper rifle from a box at the large stock gun dealer. It was all matching and very nice if it hadn't been for whatever Arsenal to pull off the bases. Despite that I bought it and since then tried to find original bases. It did threw me back to learn that No. 4 Trials bases are of different shape and have an additional examiner stamp on them, so in the meantime I acquired a set of "normal" original No. 4 T bases which I really thought about using. But I never got the way to restore it, and then all of a sudden last year I found an auction on gunbroker.com for a single No. 4 T front scope base. When inspecting it closer it really turned out to be a Trials base, carrying the examiner stamp on it! Needless to say I had to buy it and very happy to already have it here with me. While I still did not got to mount it on my rifle, I am very happy to tell you that sometimes you have to be patient and just wait for what turns up. If you don't have to permanentely mount something else (as I would had needed to do, with soldering a different base) you can in the meantime use a replacement part, but just never give up finding it. It is worth it!