WG18 - WG19, WR62 - WR51 WAVE GUIDE TRANSITION
Manufactured by Hewlett Packard as their type NP-292A, these are a waveguide transition, WG18 - WG19 / WR51- WR62, that is also known as N band to P band.
The section is approximately 6CM long.
Used but in perfect working condition, these came from a MOD test bed for the Stingray missile system.