Retired officers and staff were presented with the special award at Eynsham Hall by Thames Valley Police Chief Constable Sara Thornton.
It marked their work on the inquiry after thieves stole more than £2.5m from a night mail train in August 1963.
Ms Thornton said they had never really been recognised before.
It was at 03:00 BST on 8 August that the train travelling between Glasgow and London Euston was stopped by a gang of thieves between Linslade and Cheddington.
They broke into the High Value Package coach and made off with 120 mailbags weighing about two and a half tonnes stuffed with £2.6m in used banknotes (about £41m in today's money).
Former officers receiving the award included Aylesbury detective Keith Milner, who was in charge of exhibits during the investigation, and John Woolley, who discovered the gang's abandoned hideout.
Ms Thornton created the award especially for the anniversary and presented the framed certificate to officers in front of Police and Crime Commissioner Anthony Stansfeld and current serving officers.
What's struck me is that the focus is always on the offenders who committed the notorious crime,” she said.
“I wanted to balance that by recognising police officers and staff from 50 years ago who helped us solve [the case].
“I think also, for some of them, their work was never really recognised so they really do appreciate us taking time out to say 'well done and thank you'.”
Thames Valley Police also recognised the anniversary on Thursday by tweeting from 03:03 BST, to mark the time the train was brought to a halt, and from 04:26 BST started real time tweets of the original call log.
'Inform and educate'
Later this year, exhibitions marking the crime will also go on display in the county.
Media coverage, maps, photos and memorabilia relating to the crime can be seen on 25 August at Brill's Sports and Social Club, in Brill, a village near to where the gang's abandoned hideout at Leatherslade Farm was found.
Organisers said their intention was “not to celebrate or glorify, but to inform and educate”.
The Buckinghamshire Railway Centre at Quainton will put on an exhibition in September.