Any Info On This Double Perforated German Stamp?

Here it is a double perforated Burg Eltz 40 German stamp probably from 1977. I am looking info about this error!How rare it is to be found, its value and if in any catalog listed!Thanks in advance!

*** Edited by Staff to clarify topic title. Titles are important! ***

Welcome to Stamp Community Forum, vagosm!

This stamp is not double perforated. Rather, it has part of the previously purchased coil stamp attached because the machine is little bit mis-alligned. If you look closely at the top edge, it has the "saw tooth" pattern of the machine separating device. Sorry, no rarity here.

I have seen these coil stamps advertised as double perforations on ebay. Also, when I used to buy Germany kiloware in the 1980's and 90's, I'd find them now and again. Sometimes, you find something that looks like 2/3 of a stamp, and when you look closely, you see the "saw tooth" machine blade cut that did the damage.

Thanks a lot!I've been searching about 2 days in a row on internet but couldn't find anything!