K, I draw a representation in respect with infos provided by You on the Forum. special Thanks to EdBass. Please let me know if something going wrong, please.Thanks
Russian Baltic plywood aprox.0.75".bracing hardwood 1x1", I prefered to put the bracing for baffles outside as it can serve as support for metalic mesh as well.(I have not care too much to preserve the original fabric frame).
The baltic plywood comes in european standard as it is a product made in Europe. 12,15,18,21,24mm are standard dimension which have not equivalence into Imperial system, Also Sunn seems to use another kind of plywood. The russian come now in 13 veneers layers for 18 mm thick - that means 0.7" and not 3/4"(o.75").
I don't find this minor diferences as semnificative as I consider more important to know the quality of plywood which was used. Thanks.