They tended to be a bit scruffier on applied foot pieces but not on footless vases. Colour is not a great problem as looking at big images the method is very Ysart... so what happened with the grinding? We can only speculate...
I doubt they changed grinding wheel frequently, if at all, it is one of the best fingerprints of Monart in that is was nearly always done with a wheel of the size shown. Contrast with smaller wheels used in virtually all the Monart-a-likes by other makers.
Bases would be ground to remove high spots prior to grinding then polishing the base flat probably on a different machine to that shown,the second grind could have been done later. There do appear to be blemishes in that area....
It was a second for some reason that may still show and used for training.
A fault was noticed while grinding and grinding stopped.
Got halfway through grinding when Paul announced he was off to Caithness Glass.
The piece would then have joined the others in the store room see Ian Turner's remarks in paragraph 5 here http://ysartglass.com/Ysart/YsartPuzzle1.htm
according to which it is not Monart, just a working sample
What happened to all of the pieces still in that store after Paul had moved on? No-one seems to know but as we know several have surfaced in collections they left it at some point and were circulated among collectors.
So my opinion: made by Paul or apprentice, not finished, placed in storeroom at Moncrieff. Sold to a dealer later.