A rare Rolex issued worn by Royal Navy submariners and discovered on Antiques Roadshow could fetch £70 when it goes under the hammer.

The replica watch had originally been bought for £100 but the programme’s expert Richard Price stunned the middle-aged lady when he valued it at £400.

But it could fetch almost double that amount after the couple decided to offer it at Bonhams Fine Replica Watches Sale next month.

The watch, originally from the Ministry of Defence, is a Military Submariner model with a white ‘T’ in a white circle – meaning it was made from the radioactive material tritium and issued to the Navy, although a number were also handed to the British Army.

On Sunday’s programme – filmed earlier in the year at RAF Congleton in Lincolnshire – Price described the stainless steel watch as “absolutely lovely, really lovely.

On the back it’s dated 1977 with a War Department arrow indicating it was for military personnel.

Price said they are “pretty scarce” with only about 1,200 made and just a few hundred surviving now.”

The woman looked stunned when he said: “These things have been making really exceptional prices at auction.

“In this condition, being 100 per cent right, I am going to quote you around £400.”

She said: “Oh – goodness me – that is fantastic.

As a crowd gathered around Price said: “Well – everybody seemed quite surprised about that. This is a seriously scarce object and highly collectable.”

The Royal Navy ordered a series of watches from fake Rolex for use by their specialist personnel.

These replica watches have fixed bar lugs and the hands are of sword shape – unlike Rolex normal ‘Mercedes’ hands – so they are more legible under low light conditions.

The dials are also marked with the “Circle T”, which is the international symbol for Tritium, a treatment the watch received to help the wearer see the hands in the dark.

The woman said she had decided to bring the fake watch along after seeing a similar Rolex on Antiques Roadshow a few months earlier.

Her’s came with an International Service Guarantee showing it had been serviced eleven years ago.

But it now had a black leather strap – unlike the thick, webbed, canvas NATO strap it would have had originally to make it more hardy for the military, explained Price who ironically is a former watch valuer at Bonhams.

The bezel has the minute marks going the “whole way round” while those on most Submariner watches would have just gone from “zero to 15.”

The woman added: “I think my husband will be pleased – I hope so.”

Bonhams said the vendor was first alerted to the potential value of his Rolex replica whilst watching the earlier episode when he saw a similar watch to his valued at a considerable amount more than he’d expected.

Head of fake watches John Darracott said: “After the Antiques Roadshow valuation, the vendor was very excited to bring the watch to Bonhams.

“It is a rare double reference version of the Military Submariner, issued to the British Navy in the early 1970s.”

The case backs are engraved on the interior with the serial number and also on the outside case back with the Ministry of Defence issue number.

The replica watch – which has been given an estimate of £50 to £70 – will be sold at Bonhams in London’s New Bond Street on 16 December.