I am having a bit of trouble sorting out a recently acquired Netherlands
collection.

Using Stanley Gibbons Part 4, Perforations on the 1876-94 numeral issue are
given as:

12.5x12 (or 11.5x12) large holes
14 large holes (1877)
13-13.5 large holes (1877-89)
12.5 small holes (1884-87)
12.5 large holes (1889-94)

Now I have one stamp clearly 12.5x12 with a clear 1886 postmark
and other stamps that are clearly 12.5x13

I have had similar problems with the 1872-91 portrait of William III issue

Does anyone have a specialist Netherlands catalogue that gives more accurate
gauges?

Any help will be most gratefully received!

--
Tony Clayton