The Plilatelic Club Royal Air Force, Bruggen have issued FDCs in quite limited editions, some as small as 17 – 25 pieces per issue. Their Salvation Army FDC from 1965 was issued in a limited number of 50!! It has the characteristic Field Post Office Bruggen PM.  No. 5 in the serie was sold in May 2020 for £141, i.e. a very attractive issue. The pictured cover is number 1!!! Estimated value £150++