it seems that information about IRCs in general is difficult to find. All I know - from the German Wikipedia entry, which is a bit more elaborate than the English one - is that all coupons until at least 1999 were printed in Switzerland with the same basic design for all UPU members. Of course, the design changed over time, with this "Rome" design (introduced after the UPU congress in Rome) being the first one. According to the Wikipedia table the Rome IRCs were valid from 1907 to 1926. Your revalued coupon has a post WW2 CP42 postmark. I also have a coupon with CP42 postmark, but without overprint. I assume they are favor-canceled.
Comments
it seems that information about IRCs in general is difficult to find. All I know - from the German Wikipedia entry, which is a bit more elaborate than the English one - is that all coupons until at least 1999 were printed in Switzerland with the same basic design for all UPU members. Of course, the design changed over time, with this "Rome" design (introduced after the UPU congress in Rome) being the first one. According to the Wikipedia table the Rome IRCs were valid from 1907 to 1926. Your revalued coupon has a post WW2 CP42 postmark. I also have a coupon with CP42 postmark, but without overprint. I assume they are favor-canceled.
Manfred.