This, I'll cheerfully admit is an idle question.
On the prototype questions sub-forum somebody asked what a Bachman one-plank wagon lettered to Morris & Griffin of Newport was actually used for.
http://www.rmweb.co.uk/community/index.php?/topic/137054-pre-group-wagon-loads-for-single-plank-wagons/page-1
After much rummaging around, the said Morris & Griffin were found to the the proprietors of the Usk Chemical Works:
https://maps.nls.uk/geo/explore/#zoom=17&lat=51.5817&lon=-2.9809&layers=168&b=1
As you can see there's a fair amount of railway track in and attaching to the works, which strongly suggests that not only did they have at least one wagon but they must also have had a works loco [or two] to shunt it.
A Peckett would seem the obvious, although Avonside is also a possibility, if only because of the proximity to Bristol. Anybody able to identify it [or them] ?