Hello Frank,
A few years back the Belgian alt photographer René Smets constructed print frames similar to yours which were sold in Germany by "Monochrom".
http://www.permadocument.be/texte/LE/Exclusive/A.html
He had to abandon the construction of his elegant print frame because of high production costs.
Warm greetings,
Roger
Roger Kockaerts
PERMADOCUMENT - Atelier pH7
rue des Balkans 7
B-1180 Brussels
T/ 32 2 347 66 76
www.permadocument.be