France #261 Question?

This might be looked at like a silly question ( don't know if I should make a note or re-read something TBH)
Looking at Maury there's a few entrees for #261
Sorting the types was easy enough (I don't have a type ll...yet)
One type lll has me kind of mixed up a bit I guess
It's listed as blue. (Not sure I understand the F25 then F50 part fully, could be what I'm getting confused on)
Then there's other listed in black (also the colour chaudron I believe is a burgundy or maroon could be wrong)

Did the blue type lll have black printed over them, Making it black on blue?
I guess is my question
Agin might be something I missed or didn't fully understand

Thanks again!

I'm looking at my 2019 Maury... #261 is the 10f La Rochelle, yes? This is what I see:

Type I in pale ultramarine, with EPL and EPL in black on sheet variants
Type II in blue, and IIa in ultramarine
Type III in blue, with color essay and EPA/EPL variants

Then, several several test printings:
291A (261C) Type II in bright ultramarine only three sheets known
261B (261A) in copper (chaudron), both perforate and imperforate
261C (261B) in black, both perforate and imperforate

I don't see the Type III in black you refer to.

No 20-21
For the 261A-261C I didn't see a type written (I assumed they where type lll)
Pretty sure it's not one of them

Type ll has the open part of the 0 in 10 open at the bottom if I under that right?
And type l has the E to look for
If so it's not a type l or ll, it's not heavy spots of dark blue ink far as I can tell

It looks like black was placed above the blue (could be wrong)

May we have a scan of an entire stamp to get some idea of what this thread is about? Thanks.

Hmmm, well, the black 261 test print is all black ink. Perhaps the black-on-blue is still "blue," and was how the printer made it darker in shade? Do you have other specimens, for an ultramarine vs. blue vs. this example color comparison?

These are the ones that I have
I think the first two top and bottom are type l and the other 4 type ll

There is no such thing as black ink on blue in these stamps.What you see is in fact a depost or bunching up of the blue ink in the center of the letters. In the pic below the light colors are the constituants of the oxidized ink.
The diffderent colors found in these stamps can be sorted by printing dates.

I'll consider this solved!
I was just going to ask if oxidation would turn the blue to a black....I did read blue ink turns turquoise but still wondered
Thanks perf12