LIMITED edition banknotes will be auctioned off to raise funds for charity.

Fewer than 40 of the Bank of Scotland collectibles will be made available to aid Mental Health UK.

The polymer tenners feature rare serial numbers and a map feature which is visible when the notes are placed under ultraviolet light.

Just 18 of the total include a representation of old-style “totem” signs once used in the railway network. They correspond to the stations from Helensburgh Upper to Mallaig that are believed to have featured the curved signs, which sell for thousands at auction.

The serial numbers on the special notes also relate to the locomotive type seen in the note’s depiction of the world famous Glenfinnan viaduct.

But collectors will have to be just as fast as the steam train – online bids open on spink.com at 3pm today and close seven days later.

Philip Grant, treasurer of the Bank of Scotland said: “Bank of Scotland has been issuing bank notes for more than 320 years and I can’t express how proud we are to support Mental Health UK through these specially commissioned notes.

“If we manage to raise more than the £18,904 it cost to complete the Glenfinnan Viaduct in 1901 we’ll be on the right track.”