Measuring plate holders

I'm trying to determine the size of two plate holders I picked up last year for my Goertz Tenax Taro plate camera. 9x12 holders are too small and the ones that I need to measure are too big. Any help is appreciated. The holders in question have a lip around the holder and are made in Germany but no other identifying marks.

Thanks,

Doug

Goerz made the Tenax Taro in 9x12, 10x15 and 12x18 sizes. I just checked a Zeiss advert for 1927 - the comanies had merged but were still making their own cameras,

Ian