(28 Sep 2020, 9:49 am)ASX_Terranova wrote It looks like one of the blyth runs uses 1502, is a pulsar standard for the 57/57A. 
Also that long gap is a bit strange especially with scholars and works around that time.

Anything can turn up on the Blyth run from what I've seen. With it just being the one run I'd imagine it's just whatever is easy to take from the depot, as there certainly doesn't seem to be a set board for it. 

The gap in Ashington workings is only for driver breaks. One board comes off the 17:55 57 to Ashington, then goes back out onto the 19:57 57A to North Shields. The other comes off after the 18:25 to Cramlington, then back out onto the 20:57 57A to North Shields. The Blyth run does the 18:57 to North Shields and return (essentially covers the gap between the 18:25 and 20:57 Ashington runs).