Remember that Wratten filters came in CP and CC varieties. The CC filters were not as high in quality as the CP filters. It should be specified in all cases, which filter you have or want.

All of the above color filters in post #28 came in both types and in increments of 0.10 so that there was a 0.1Y, 0.2Y, 0.3Y, 0.4Y and 0.5Y as an example. There were R, G, B, C, M and Y filters and the sizes varied up to 8x10 sheets.

The ND filters came from 0.1 up to 6.0 and were in increments of 0.1, 0.15 or 0.30.

Kodak made filter holders in 2" and 3" sizes for use below the lens (CP filters) and the larger filters (CC) were intended to be sandwiched in with the negative in the holder or above it. These larger filters came in small sizes but also in sizes of 5x5 and larger.

The filters were cast dye in gelatin on a transparent support. As such they are quite fragile and subject to damage.

There are also the Wratten cutoff filters for tricolor printing. The WR 98, 99 and 70 come to mind as the sharpest cut of them all and the ones that give the highest purity in color when used in making color prints from negatives or slides regardless of the method used for producing the print.

Just some old time information FYI in a spare moment.

PE