An armour-plated "battle bus", believed to have been used by former prime minister Margaret Thatcher in Northern Ireland, is to go under the hammer.
The 28-tonne bus was thought to have been built in the 1980s for a visit by Mrs Thatcher, before being used to transport troops, auctioneers said.
It has a blast-proof floor, armour-plated glass and was thought to be chemical, biological and nuclear-proof.
It is expected to fetch £10,000 in Towcester, Northamptonshire, next week.
Auctioneer Jonathan Humbert said the bus, which can hold 35 passengers, has just 28,000km (17,398 miles) on the clock and it has its own auxiliary generator and air supply in case anyone attacked it.
It also has a Foden chassis, a body by Glover and Webb and is powered by a 12-litre Rolls-Royce engine, Mr Humbert of JP Humbert Auctioneers said.
The sale comes from a private vendor who bought it from a research and development company, which in turn had bought it from the government.
"This isn't a good-looking vehicle by any stretch of the imagination - but is of social and historical interest," said Mr Humbert.
"It is an irreplaceable one-off, an iron bus for the Iron Lady."
The bus will go under the hammer on 21 February.