GWR Tender Water Level Gauge. Which Tender and Loco?

Churchward and later 4,000 and 3,500 gallon well tank tenders were rated for 7 tons of coal. 3,500 gallon flush tank tenders were rated for 5.5 tons, 4,000 gallon flush tank tenders for 6 tons. The very limited information I've seen for the high sided tenders doesn't suggest they had a different official capacity, but it surely must have been possible to pile more on, although I might speculate that the practical limit might have been the amount of coal that "self-trimmed" onto the footplate rather than the sides. What confuses things even more is changes in service. I've seen a suggestion that some well tank tenders were given replacement flush tanks, but retaining sides looking like the well tank ones, so there may have been all sorts of mixes and matches.

 

I've attached a picture of No. 6391 (the other possibility), which appears to have a similar tender to No. 6385, but it's difficult to tell given the angle from which the picture was taken.

So, according to Jimc's drawings we have:-

6807 Post 1926 3,500 gallon flush tank.

6385 and 6391 High side 3,500 gallon well tank.

7324 Low side pre 1926 3,500 gallon well tank.

All I have to do now is find examples of each type of tender in preservation and see if I can eliminate any of them from my search because they don't have an A4205 water level gauge.

Interestingly the tender being used for the Saint Project uses this water level gauge, but is of yet another type.

 

I think the gauge has to be from a well tank tender. Reason is the relationship between volume and water depth on the gauge varies widely, as you'd expect on a well tank tender that changes drastically in shape at different heights.
There are no high sided tenders surviving, but in any case I'm reasonably confident that the actual water tank was the same on low sided and high sided tenders. The GWS new gauge being much the same confirms that.

The 3,500 gallon well tank tenders weren't drastically redesigned, but evolved steadily. They were essentially much the same from 1905 to 1926 with many components the same or at least interchangeable. At first they had shorter coal fenders, and the tender to be used on 2999 has had shorter fenders made and fitted. They were later all given longer fenders, and I think all surviving well tank tenders have those (except 2999). No original high tender sides have survived to my knowledge.

Looking at preserved tenders is not very reliable because so many have had new tanks in preservation, and indeed Swindon mixed and matched components. The tender for 2999, for instance, is running with replacement frames which are of the post 1931 design. The tender on 3822 is the only one at Didcot with earlier type frames I think.

The records files at Kew say that the same drawing (41746) was used for water indicators from lot A79 (1910) through to lot A112 (1926). Assuming you have one of those that would be any tender from n 1786 to no 2383, plus any earlier tenders that gained that water indicator later on in life. I think you're really going to struggle pinning it down much further.

That tender with 6391 looks like a standard (low side) one rather than a high sided to me, but its not the easiest of angles. I'm sure its a well tank type though.

I think you can reasonably safely say its from a pre 1926 3,500 gallon well tank tender which was last fitted to a 2-6-0. Further than that I don't think it will be possible to go: my guess is the tenders on all 3 probably had the same indicator. Of course being a GWR tender it was probably fitted to a host of different locomotives over the years, there were 639 of these well tank tenders, and there must be few Churchward standard classes that never ran with one. The only thing you can guarantee is that it never ran with a King or a County.