OzzyO
Western Thunderer
I read it as being two sheets - one of which varys between 16.5 and18thou - the second sheet is a consistent 22thou.
Yes rereading it I can see how it should be read, but it does seem odd that the sheet thickness should vary by 0.0015", all I can say is that it has been rolled wrong if it is going from one side to the other, or it could be that the rollers are worn and in need of some TLC. In that the centre of them has worn.
Saying all that, the etcher should sort that out as he/she bought the metal stock and it can affect the work that they are doing not just in the model making businesses, if for instance it was going to be for a short run of printing plates. I'm just guessing that it's the brass sheet that is out of thickness.
OzzyO.