Ah, one of the famous Czechoslovakia Hradcany stamps. I really like these stamps.
Robert, that line is probably constant, in the same position on every sheet. As a matter of fact, pretty well all values of the set can be plated by position, every stamp in the sheets have unique identifiers.
The stamps were printed just after WWI and Czechoslovakia's independence. Printing supplies were scarce.
Nice Hradcany plating site here:
http://www.knihtisk.org/hradcany/200c/plate.htmDirect link to your stamp - see if you can find it's postion.
