Stumped on this one.
This 1k stamp does not appear to have the colored vertical lines suggesting design A3, but there is no 1k listed for design A2. Definitely watermark 135 (crown in oval). Is this just the nature of the 1k stamp?
This 5k image (Scott #25) shows very faint colored vertical lines (that I could only see after scanning in at 600dpi), but I'm pretty sure I'd be able to tell if they existed on the 1k.