Unless you've room in your house for an Olympus 593 or a functioning 'droop snoot' then, as far as Concorde paraphernalia goes, you can't really beat a genuine Machmeter.
Of course, with a fleet of only 20 aircraft there aren't many kicking around. But if you're really determined to have a pretty exclusive bit of kit on your sideboard then you'll have your chance in a couple of months. But it ain't gonna be cheap.
"Very few Machmeters appear in auction and some have made several thousand pounds in the past," says auctioneer Simon Jones, of Somerset auction house Lawrences which is selling the instrument from 'Alpha Delta', British Airways' aircraft 210, on 6 May.
Lawrences says the device was a retirement gift to an avionics engineer on the Concorde fleet, Peter Gravestock, who also worked on BA predecessor BOAC's Vickers VC10s and several other types.
Reserve price? If you have to ask...