Baltimore & Ohio Sentinel Fast Freight Service, when did it end?

[SRen]

Does anyone know when the B&O dropped Sentinel Fast Freight Service?  When did the last of the distinctive silver and blue box cars lettered for this service get repainted standard box car brown?  Did any silver and blue box cars make it into the late 1960s before being repainted?

S Renchin 

[PBenham]

Sentinel service was LCL traffic, so it was toast before the 50's were over. I recall seeing a Sentinel box at East Salamanca in the very early 70s, but it was in very rough shape.