The guys above have pretty much said it all!
Moore and Wright are / were the British answer to Starrett. They have historically made a huge range of items, and quality was on a par with Starrett too, although some of the tools differed in style!
I have several squares, calipers, Micrometers of various types, and Verniers by Moore and Wright and all are superb, however... most of mine date from the 60's and 70's, and some much earlier! Later stuff isn't quite as nice, but it's o.k. They don't currently offer anywhere near the variety of tools that they used to.
Much like Starrett, some items are now made in China, and I'd personally avoid 'em!
Anything Sheffield made is probably fine however, and the last squares I saw still looked pretty decent. 'Class B' squares are considered 'workshop grade' and are pretty decent but also affordable. About 99% of the squares you find are 'workshop grade'. 'Class A' are 'inspection grade' which means uber accurate but also uber expensive!
Personally I pick up used Moore and Wright if I need any - the volumes produced are incredible and you can usually find what you need sooner or later. Stuff like Calipers, Squares and even micrometers are very durable so I have no qualms about buying used!