Tell Me About This R13

I'm just a beginner on revenue stamps and would like to start adding a small group from an ancient approval book I bought years ago from an estate to a easy stamp album i'm making. Better late than never eh? There are several R13s, 2 are a paler blue while the 3rd is darker more prussian blue.This one looks unused to me but lacks gum. It's still hinged into the book.
I don't have access to a scott catalogue at the moment.
is this a double transfer? or was it inked with a little too much exuberance? ballpark value? Scott number correct?

I do not believe this is a double transfer, just inking anomalies

It's the milky blue shade of R13c, similar to the milky blue of R97. I personally think there should be three color listings for R13 in the same manner of R97, but every time I bring it up, there's resistance.

In my opinion the milky blue shade is just as common as the normal blue. It's only the ultramarine (R13e) that is truly scarce.

Here is an image of the 3 R13 color shades scanned together. From left to right:

1. Ultramarine (R13e)
2. Milky blue (R13c)
3. Blue (R13c)

Thanks for your help. So there is no designation for the milky blue vs the regular blue? They're both R13c's? Interesting as the colors are very distinctly different. Were they issued gummed? BTW If you right click on the image and open in a new tab the image is much bigger. What would value be for this one vs a pen cancelled one?

It looks like the paper was a bit too wet in spots when printed. Scott will never add the common shades to the first issues; it would add 2 more pages by itself. There is no question that a deliberate change occurred during the run of the first issue, the dark shades were made lighter and the light shades were made darker. This was in an attempt to make cleaning and reuse more difficult.