1970 Anniversaries - Philart - Sir William Herschel H/S + Slough CDS

Lovely Philart cover with the full set cancelled by the Sir William Herschel H/S + Slough CDS.

This H/S is not known to exist on an Official cover, and all the examples I have ever seen are cancellewd with this H/S and the CDS in this format....

Code: 57289