(16 Aug 2019, 1:21 am)Washingtonian wrote
I might be wrong here but I think the A in 49A is for the Anti-Clockwise part of the route, while the 49C is for the Clockwise part of the route. That's why I think they use A and C, instead of A and B. I'm sure this was the case for the old Silver Arrows Sunderland - Washington services 2A and 2C. This numbering used to annoy me too until someone explained it.
There aren't circular parts to the route. Historically, when they were all in existence together:-
49 Gateshead to Winlaton (via Blaydon and Black Lane)
49A Gateshead to Winlaton (via Blaydon and Gibside View)
49B Gateshead to Winlaton (via Blaydon, Hazel Road and Parkhead Estate South)
49C Gateshead to Winlaton (via Clasper Village, Wellington Road, Blaydon, then 49B route)
49C ran Evenings and Sundays more regularly, when there was no 95/95A or 64.