The following extract is taken from G.B. Official Perfins by T. A. Edwards and B. C. Lucas (1984)
In August, 1895, following the example of the Board of Trade, a perforator (Type I) supplied by Slopers was brought into use to perforate the then current postage stamps with the initials HM/OW. Official documents state that 2,400 1/2d vermillion (SG 197) and 3’600 1d lilac (SG 172) were perforated and made available for use in the Department’s various offices. In October that year a new perforator (Type II) also supplied by Slopers was introduced which produced the perforation (crown)/OW. This was similar in general design to the Board of Trade perfin but not so finely produced. In fact the Type II Office of Works perfin was a very roughly drawn crown which compares badly with the finely proportioned Board of Trade crown. (The illustration in reference (viii) is in error). It is reported that a further 2,400 d 1/2d and 3,600 1d stamps received this perforation.
The perfin (crown) / HMOW reported in reference (vii) has not been seen by the authors and is presumed to be an error in reporting.
The Type I perforator was introduced in August, 1895 and the type II only two months later so both can be found in use over the same period. The perforated stamps were withdrawn from use on the 24th March, 1896 when the overprinted stamps (SG O31 and O32) were brought into use, but it is possible that some perforated stamps were used after the introduction of the overprinted examples. The only stamps perforated by this Department were the 1/2d vermillion (SG 197) and the 1d lilac (SG 172) and no record can be found of perforation of higher values, although higher values were overprinted.
The very small number of known examples of these perfins makes it difficult to be sure which postmarks may be found on them, but they could genuinely appear with 1890s type provincial postmarks of the assistant surveyor towns (Bristol, Leeds, Edinburgh, Glasgow, Liverpool, Manchester, Birmingham, Southampton) and it is possible that London SW postmarks may be found. However, any use on London mail would be unusual as the inland mail from London would be franked and the foreign letter rate was 2 1/2d. There may have been some use on parcels from London which would bear London parcel post obliterators. The only used example recorded by the authors was postmarked ‘Liverpool 11th February, 1896′.
There are very few known examples of this perfin and they have exchanged hands at auctions for large sums. This may have encouraged forgery but there have been no reports of such items. Nevertheless, care should be taken in purchasing examples of this perfin both off and on cover. The authors know of an example postmarked in Newcastle-on-Tyne dated the 22nd March 1897. This may well be a fake but the perfin is apparently identical to the genuine examples.
(i) “SG Specialised Catalogue (part 1)” p. 173
(ii) “Kohl-Briefmarken Handbuch (2nd Ed.)”
Verein de Freunde des Kohl-
Briefmarken Handbuchs. Berlin Vol 3, 1931
pp 823 — 825
(iii) “Stamps” July 1982, 3 (5)
(iv) “Gibbons Stamp Weekly” 21st December, 1907 6 (25)
(v) “Stamp Collecting”, 22nd March, 1963
(vi) “Catalogue of Official Perfins” by M.E. Thornton pub. SEPS
(vii) “Philately”, 4th November, 1946
(viii) “The History of Security Printing and Perforation of Postage Stamps” by Chas. Jennings. V pub. SEPS (1967)