1975 (08) Railways - PO - Darlington 'Ticket' H/S + Snowdon Mountain Railway Cachet

Unusual Post Office cover............

Darlington 'Ticket' H/S + Snowdon Mountain Railway Cachet.

Cover has got 'sunburnt' on the elft side, and I don't understand why a Snowdon Mountain Railway cachet is on the cover as I am not aware of any link between Darlington and Snowdon !

Code: 60963