15 Cent Grey No Perforation At The Base

Hello,
I share those images because seems to have no perforation on a side and some trouble on other sides.
Seem to have a coil line too. Is not printed on flat sheet ?

Thank you!

The line at the bottom edge of the stamp is an artifact of the printing process.

For a discussion of these lines and how they occur, check this article:
https://stampsmarter.org/learning/I...reLines.html

While it focuses on the lines in red and green stamps, it is applicable to the issue on your cover as well.

With various searches and people ignoring punctuation, I tried several years ago to entice Don to change his title to something more direct like "Red and Green Lines are not Errors and are Seldom Rare or Valuable", but to no avail. Beyond that, the article could also be expanded to differentiate between lines actually on the plates (typically flat and offset printings) versus joint-line ink accumulations (typically rotary printings), since various lines on the finished postal product often have different purposes or causes, etc.

OK thank you !
Ad what about the perforation? usually all the edge are perfored in the same way

The bottom side is a natural straight edge as noted in the article linked above.
The right side perforations have been damaged by insects, most likely silverfish. The left side has some damage also.

Thank you to all !

If you haven't checked for it, your stamp on the cover is a Scott #514.

Dear Al E. Gator,
thank you for the help and sorry for the my late answer.