Is This A New Caledonia #2A Or #6A? How Can I Differentiate The Two?

I have this inverted overprint stamp in my collection. If it is a 1883 New Caledonia #2a, it is a several hundred dollar stamp, if not more. But the #6a stamp is of the same design, color, and inverted overprint.

How can I properly identify which one it is, the #2a or the #6a?

Help please! thanks.

Value line is "05" on 2a
Value line is "5" on 6a.
(Horizontal spacing of NCE is also different.

Actually, the value line is "5" on both 2a and 6a. #3 is the one that reads "05".

The difference between the two stamps is the spacing in NCE. #2/#2a have the letters close together. #6/#6a have the letters far apart. Your stamp is #6a.

Hmm, Scott is not clear on this then. Agree it looks like a 6a.

Yeah, the illustration of the surcharge for "Nos. 2-5" in the Scott catalog shows a #3, because that's the cheap stamp in the set. I see how it could give the impression that the leading zero might be there for all of the stamps, but it isn't; the distinguishing feature in the two overprint types is the kerning of the letters.

The catalog would be much clearer if they described the overprints with something like "Overprint With Widely-Spaced NCE" and "Overprint with Narrowly-Spaced NCE" in the listings.

Michel #2 and #6

For grins, I pulled the 1920 Scott catalog off the shelf. (All the world in one tiny volume!) If provides 3 illustrations. So much clearer than the current catalog!