Help Identifying These Sheet Film Notches

[AidanAvery]

I just acquired a 3x4 Graflex RB. When I was examining the film holder, I found that there was already sheet film inside. The camera hasn't been used in a number of years, so I have no idea when it's from. I took one out to help identify the film, and left one sheet in the holder unexposed (which I hope to shoot after identifying the film).

Is anyone familiar with these film notches? It doesn't seem to match any of the notch patterns I can find online. Again, this is 3x4 film.

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[AidanAvery]

Looks like it might be FP4plus
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[AidanAvery]

Ahh, nevermind. I think HP5 plus is more likely, given the orientation of the notches in relation to the corner.
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[koraks]

Neither would be likely since this has all the looks of a C41 process film. Note the orange/brown base...

[Dugan]

Those look like Fujichrome notches.

[AidanAvery]

Thanks to both of you for the input. Since I'm mostly unfamiliar with color film, I didn't recognize that the base indicated that it was likely color. As it turns out, by this morning I had shot and developed the sheet to test the camera. I treated it like HP5 (since that was my best guess at the time). 5 mins in HC-110 Dil B. Worked fine, at least enough to confirm that the camera is functioning and there are no light leaks. Since I didn't feel 100% positive about the film, I also cut down a sheet of Tmax 400, then shot and developed that too, just to make sure that my shutter wasn't lagging. Looks like all is good!

[koraks]

So out of curiosity, were there any edge markings in the developed sheet that tell something about what it is.?

[AidanAvery]

No markings, unfortunately. It also turned out to be slightly undersized, so I'm guessing it had been cut down from 4x5 and the markings were lost in the process.

[Dugan]

Looks like HP5+ .... although the reddish anti-halation coloring threw me off.
Probably from an ULF program run, might be factory cut to size.

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Figured I'd include development times. :)
Why not?

[koraks]

Could be some color process film, maybe duplicating film or so.

I really don't think it's HP5+ or any other b&w film. Does the developed sheet still show the orange mask? If so, it's really a color stock. I don't know of an antihalation dye of this color, but who knows...?