Three letters to Greece
From 26 April 1976 the postage rate for letters to Europe was 10p for 20g, so this letter, without a clear UK postmark (see update below) but with an Athens arrival of 31 May 1977, was correctly prepaid with the standard 10p light orange-brown.
On 13 June 1977 the rate was increased to 10½p. This letter - with the Athens arrival mark of 4 September 1977 on the reverse, and a violet boxed C85 (or 685) cancelling the stamps - was prepaid with the same 10p stamp and an additional ½p stamp.
My thanks to PA for this additional information, which coincidentally identifies the postmark on the above cover as Reading:
The cancellation is actually 635. These rectangular ‘killers’ were applied to uncancelled stamps in the Reading Foreign Section in the 1970’s. i.e the letter could have been posted from anywhere in the South East. Reading FS was in a separate building from the MLO at that time.
The third one, to the same addressee but from a different sender, uses the shortlived 10½p yellow, issued on 25 February 1976 and replaced on 26 April 1978 with the grey-blue version. Finding covers to Europe franked with a single stamp for the right rate is not easy and the destination of Greece rather than, say, France or Germany is even better.
The other international cover I bought today is a gem: not pretty, not tidy, but a gem of an exercise in rate research. This is an airmail insured packet to South Africa, prepaid £3.35 with the use of 3 x decimal £1 stamps, a 20p dull purple, and 3 x 5p pale violet, and clear New Barnet Parcel Post marks dated 23 December 1976. My initial thought was that insurance must have been expensive, but in fact it is only a low fee.
My source was the website of the Great Britain Philatelic Society (GBPS) which has an excellent series of postage rate tables for inland and overseas mail including 'special services'. In these tables I found that insurance fee for this date was 65p for up to £175 and 70p for up to £210, so this packet insured for £200 needed the 70p fee. The balance of £2.65 was obviously the postage, but how is this arrived at?
The airmail small packet rate tables show 130g is 49p, and each additional 10g is 3½p. 3½p doesn't divide evenly into £2.65 (=75.71) so it probably wasn't a small packet, although 130+ (75x10g) 750g is still within the limit of 1kg for a small packet. Curious.
The GBPS website doesn't include all the parcel post rates - for some periods there were many different rates for the countries around the world and in some periods they changed more than once during the year. But the site does reference the publication of amendments to the Post Office Overseas Letter Post Scheme in the London Gazette, the official public record for certain legislation, regulation, and official notices, etc. Here, I found that the rate for an Airmail parcel sent outside Europe varied from £2.20 to £3.60 for the first ½ kg, depending on destination, but the rate for South Africa was... £2.65: the packet was prepaid exactly as it should be, as you would hope for something posted over the Post Office counter!
When the basic inland postage rate was only 8½p for second class, a £1 stamp would almost certainly only have been used on parcels. To find three on one cover - even a slightly damaged cover - is very pleasing!
(Click on the images to see a larger version.)