A complete set of sheets for the Russian 1866-1875 series is to cross the block at Spink London on July 20 with a valuation of £40,000-45,000 ($61,539-69,231).
The lot is one of only two surviving sets of the issue extant.
In total there are six perforated sheets, each made up of four panes of 25 stamps, valued from 1k through to 3k.
While the design of the issue remained more or less the same as earlier stamps, advances in technology led to the introduction of watermarks.
An 1897 Chinese large figure revenue surcharge is another highlight, with a valuation of £20,000-25,000 ($30,765-38,457).
The lot is offered in good condition, without gum, and displays strong centring and colours.
An 1898-1908 Rhodesia £20 yellow stamp carries an identical estimate of £20,000-25,000 ($30,740-38,435).
It's offered in mint, unmounted condition and is described as "a great rarity of fine appearance and a showpiece".
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