ABT suggests that very early wagons were dumb buffered, with wooden solebars, and built AG Worcester & Saltney from 1868-71. There was a drawing but no diagram number, issued in 1917 from Swindon, of which there’s a small version in the book, but that has conventional buffers and is a single plank open with wooden solebars. The sketch appears to match the first photo in the chapter, wagon 5141, apparently built 1870, the photo is believed to date from the 1890s.
it doesn’t look like either of your photos. The lettering on your first wagon would be post 1904. Prior to that date, it seems that the G.W.R. was widely spaced, and on the lowest plank, below the Tare weight.
there is one 3-plank dumb buffered wagon photo (plate 341, pg 272) which has a single (wooden) brake block, the G.W.R appears to the left of the door, and above the “to carry”. It has 5-link couplings and was built before 1870.
hth