1867 Brown-lilac stamp could bring £18,000

The £1 rarity will auction alongside a Penny Black pair in London tomorrow

Spink's sale of rare stamps in London tomorrow includes a classic British Ceylon overprint, as we've mentioned already. But the most valuable pieces are from Great Britain itself.

Firstly, there is a fine horizontal pair of Penny Blacks, from row C of a sheet created by Plate V. With some of its original gum still present and good margins all round, this remains fresh and attractive despite light toning.

There is another reason why a bidder might be keen to get their hands on it: it was owned by the greatest stamp collector of recent times, Bill Gross, until 2007. It is estimated at £15,000.

Also appearing in the sale are two high value stamps from the 1867-83 series: a greenish-grey 10 shilling stamp and a brownish-lilac £1. Both have a small part of their original gum.

1867-83 10 Shilling Greenish-Grey stamp

Each has a minor flaw: the £1 stamp has the faint trace of a diagonal bend whilst the 10 shilling piece has a minor abrasion by the chignon of Victoria's hair. Nevertheless, both are exceptionally appealing, the 10 shilling piece in particular having brilliant colour.

The Stanley Gibbons prices for the two stamps are £50,000 and £80,000 for the 10 shilling and £1 respectively, but here they have guide prices of £12,000-15,000 and £15,000-18,000. This indicates that they might be particularly worthy of consideration as a tangible asset.

1867-83 brown-lilac £1 stamp

The £1 variety was also once the property of Bill Gross, and before him it was in the collection of Alfred H Caspary, whose collection of American provisionals was legendary.

Those interested in collecting classic British rarities will be interested to know that a Tyrian Plum is currently on the market.