As an observation: As the grades increased normally the pattern size decreased but you also find fewer deviations in the pattern and few or no end welds the length of the tubes. Baker's Batavia guns almost always show an end weld somewhere. I don't think they cause a weaker tube but they aren't worth bragging over.

Within a given Maker the difference in definition could be pattern size. Where Fine & Extra Fine defines the size of the pattern, thus smaller wires and many more of them within an area of the tube. I missed buying this Ithaca Flues not long ago. It was a late Quality #1 gun with these mismatched Damascus tubes:


The lower(LH) tube has the standard(size) pattern. The upper(RH) extra fine pattern.





I own an Ithaca, Lewis, Quality 2, that has Extra Fine pattern from the breech forward approx. 5", then changes to Fine pattern for the remainder of their length. I can try to take pictures if it is of interest.

John