The RA in the ring ... factory ID stamps indicate the Rootes Securities factory. They made Blenheim, Beaufighter and Halifax aircraft. If it would be the Stirling the stamps would be in oval but not in round and the ID letters would be SB or SHB for the Shorts factory. The part prefix 57 was used for Halifax MK.I.
The part 571037L? - Halifax I. drawing 1037, L - electrical and general equipment, 1? ... if it is - the port side.
The part 571703C1 - Halifax I, drawing 1703, C- fuselage structure, 1- port side.