What is a #10 Blue/Violet filter?

I've seen such a thing on various lists of Series filters, e.g. https://filterfind.net/Series_6.html but cannot seem to find any information about it. All the tables of Wratten numbers I can find seem to skip #10. Is this even a Wratten number at all, or another designation that's equivalent to something like a 34A or 38A?

Ultimately I'm looking for a shortpass blue/violet filter that cuts off somewhere around the same wavelength as a Yellow 8 cuts in, but is less opaque than a Blue 47.

Even a Wratten 34A might be hard to find today. It won't come cheap if new. Note that the 34A has two transmission lacunae to its spectral distribution, the 36 only one; but a 36 is probably denser than a 47 blue (not 47B blue). Just call or e-mail him at Filterfind with your question. It could be a Euro rather than Wratten designation. He's got quite a selection of odd filters in stock in a warehouse room adjacent to his personal painting studio.