Polish złoty

"Ł" was a type of currency.

At some point, the Ninth Doctor tried to purchase an issue of Classic Rock from a W H Smith's with a Ł10 piece. (PROSE: Have You Seen This Man?)

Behind the scenes
While not fully titled in Have You Seen This Man?, the currency is. However, later revisions to the website that hosted Have You Seen This Man? changed the currency to a GBP "£".