It's quite clear from the photos above that this ICA Ideal uses slide in holders, the focus screen pops open for focussing but has to be slid out . They aren't quite the same as the ones I have, seems to be a wider lip
Originally Posted by Mark Layne
The best place to find 9x12 holders is German ebay.de - it's where I've bought all mine the. Login etc is identical whatever front end as it's a common database. However items don't always map across to each version properly. Search 9x12 under Foto & Camcorder there's not many listed at the moment, they are best bought as sets of 3 in a small case. You will need patience waiting for the right ones.
Quarter plate holders would have been sold mainly in the UK, but both formats were sold and some sellers get the sizes wrong.