Hi Len,
Does the barrel have the raised section where it fits in the cocking linkage ?
I can't say I've noticed any with a step such as you've shown.
I have a couple of Service barrels that are numbered to a gun, with the calibre marked in the correct location in what appears to be original typeface, that are apparently not original Webley barrels.
I haven't looked closely at any interceptor sears, but will check and see if any of mine have a rounded trailing edge.