identify the links

[CINDERS]

I have tried a Nato round in them and wont fit, the person I procured these off many years ago informed me they were links from an aircraft armed with the 303 round hence why I put 2 singles one of each to show you.
Other aircraft news bit there were 303 rounds that were specifically designed for aircraft only with 3 - 4 stabs in the primer hole to hold the primer in place, there were reports of the Spits pulling 10G but tended to crinkle the wings a bit though Reginald Mitchell designed a plane that even today endures and inspires