@Symptoms - whilst searching for info on the Netherton Colliery banner I noticed this banner - SLEEKBURN "A" - you posted. The West Sleekburn pit, as you also posted, has a different banner.
It may seem obvious, but rather than just assume, do you know if this was the Bedlington 'A' pit banner?
I know Bedlington Station was originally the village of Sleekburn, before the Bedlington railway station opened, but I have never seen the Bedlington 'A' pit named anywhere, including the Durham Mining Museum (DMM) site, as Sleekburn A.
The DMM has Bedlington 'A' pit opening in 1838 and the Disused railway station site has this info on the railway station :-