The Stamps Of Guernsey-Alderney.

Locals or Bogus.
Not listed Stanley Gibbons or Scott
No Steiner Pages.

Commodore Shipping Company

This Company produced stamps for use on the parcel service they operated between the islands. The stamps were used on the Alderney route in the 1960s, and on the Sark route in the 1950s and 1960s. These form an unusual collection.

https://www.ciss1950.org.uk/stamps/

Commodore Shipping Company.

Delcampe
https://www.delcampe.net

Stamps inscribed Guernsey Alderney overprinted for the 1971 Postal Strike

The 1971 United Kingdom postal workers strike was a strike in the United Kingdom by postal workers between January and March 1971
The strike overlapped with the introduction of decimal currency in the U.K

A range of officially licenced and unlicenced private posts operated during the strike to fill the gap left by the withdrawal of official postal services. Some were genuine commercial services that provided local, national and international deliveries, but many were set up by stamp collectors and stamp dealers to provide philatelic material for collectors.