QEII Machin Definitives laboratory research and development files examining the resistance of printed phosphor and inks to various solvents 1970-71 incl. seventeen pages of imperforate £p definitives (236 stamps and 18 controls) and a page of four examples of the 2d value perforated, each sheet with accompanying evaluation. Also files investigating inks for FDC cancellation of 1970 Philympia issue. Includes three unstamped Wordsworth FDC's and seven High Value FDC's with selection of 10p, 20p and 50p stamps (14 in total), all showing many SPECIMEN Impression coloured cancels with a letter and specimen cancel from ink manufacturer. Also 13 pages (A5) of interdepartmental notes and memos of 1972. This lot is accompanied by two pages of notes from Mr Norman Potter, a research technician in the PO laboratories in Islington with details of this material, dated 26 Dec 1970. Numerous stamps in small packets relating to work on phosphors. 'Hot off the press' notes on daily samples and internal PO envelopes used for distribution. Uncut sheet of 40 front covers of 30p Curlew booklet (folded in half). A fascinating archive which must be viewed to fully appreciate. (Image)