Australia #415-417 (SG#401-403) $1 to $4 Navigators, 1966-1973 Decimal Definitive Issue, A Specialized Lot of Fine NH and VFNH Stamps
A fine NH and VFNH group of 7 stamps, comprising the $1 to $4 navigator stamps from the 1966-1973 decimal definitive, including many different unlisted paper varieties, and differences in the strength of the Helecon coating on the paper.
The Australian equivalent of tagging is called Helecon, which is a chemical in the zinc sulphide group that fluoresces orange-red under long-wave UV light. The very first stamp to be issued with Helecon coating applied to the paper was the 11d Rabbit Bandicoot from the 1958-1964 definitive issue. Later, the 5d orange-red Queen Elizabeth II stamp from the 1963-1966 issue was issued with the Helecon incorporated into the ink. By the end of 1965 all stamps issued had Helecon applied to the paper. On this issue, some stamps are found with a uniform coating on the paper that glows orange-red, while others have the paper impregnated with Helecon, so that it appears greyish white from a distance under UV, but under magnification, tiny orange-red dots can be seen on the surface of the paper.
The comparison picture shows some of the differences that can be found on the high values of this issue.
Gibbons lists the basic stamps at 28.50 pounds (approx. $57) for VFNH. The stamps here grade between 65 and 84.