New Zealand Postage Due. Help With Sg Number

Yet again, my Scott's is useless. I believe both of these would be classified as pairs of Scott J17. The first pair has nice, clean perf holes and a postmark date of Sep 23, 1931. The watermark is normal, so all indications are that it is SG D34. There is an interesting fault to the left value circle, as shown (probably a minor printing variety). Can you confirm SG number?





The second item is also Scott J17, but a much earlier year. The postmark reads July 12, 1910, watermark sideways, so I put this as SG D21. However, I note the perf is 14, but the hole punches are extremely small. Maybe this one was at the bottom of the punching pile? Anyway, does this appear to be SG D21? Thanks in advance.

Your reasoning looks pretty well spot on, I would agree.
A real specialist req for confirmation.

The perfs on the D21 look constant with these at

http://www.classicstamps.co.nz/

Carmine vs Rose Pink is a tickler.

The pairs are SG D21 and SG D34 respectively.

If you look at the frame just left of 6 o'clock, you will see in D21, the frame is smooth, in D34, the frame has a little nick in it. This defines die 1 and die 2.

D17 - D22 are die 1, D23 onwards are all die 2.

Your D34 block is easily identified as it is perf 14 x 14, the only die 2 in this perf. All others are perf 14 x 15.