that were printed in 1941 but remained undelivered to Hong Kong until 1946. The reign of Queen Elizabeth II saw several significant changes to stamp design. While the first series (1954) retained the design of the George VI stamps, the second series (1962) saw significant changes. The series, designed by Chinese Cheung Yat-man, did not feature the traditional frames of the previous stamps, instead featuring a frameless portrait of Queen Elizabeth II by Pietro Annigoni. The larger values were printed in colour and in a larger physical size. This series is nicknamed the "military attire" (「軍裝」) series by local stamp collectors. 1962 saw the release of the first officially designed envelopes for first day covers, marked with "OFFICIAL FIRST DAY COVER", for the 100th anniversary of the first postage stamp of Hong Kong. Prior to 1962, there were no official designs other than the postmarked date, and envelopes were designed instead by hobbyists such as the Hong Kong Philatelic Society and the China Philatelic Association. Commemorative stamps with Chinese themes were first issued in 1967, featuring the Chinese zodiac. The bauhinia flower and Hong Kong's coat of arms were also incorporated as the key features on two denominations issued in 1968, the first time that local themes had been integrated in the territory's definitive stamps. The addition of Chinese and local themes and features, along with designs by local Hong Kongers, became increasingly common in the 1970s and onward. The third series (1973) featured a reproduction of the bas-relief by Arnold Machin, a design feature that would be retained in all following new series. The fourth series (1983) saw the introduction of fluorescent security markings in a design by Arthur Hacker. The fifth series (1987) featured 15 stamps. In 1988, the fifth series was reprinted with a change in shading on the Queen's lower lip. These were reprinted in 1989, 1990 and 1991 as the stocks for certain values were running out. In the early and mid 1990s, as the Handover of Hong Kong of 1 July 1997 drew near, British-themed stamps were slowly being phased out. The sixth issue (2 September 1996) was the last set of stamps featuring Elizabeth II. This led to an "explosion" of sales and stamp collecting in the local stamp market, with many hoping the stamps would sell for a profit in the future. On 23 May 1996, it was announced that all stamps