LNER and BR (ER) Models 15
No. 1504 is an S69 Class 4-6-0, designed by Holden for the Great Eastern Railway, and seen here in that company's post World War One light grey livery, with large numbers on the tender sides replacing the original GER lettering. After the Grouping in 1923, the LNER reclassified these locos as Class B12, and later rebuilt them with Gresley round-topped boilers, replacing the originally-fitted Belpaire-firebox version depicted here, and also removed the ornate valances. I've no idea of the origins of the kit used to produce this model, as the already-built loco was bought second-hand at auction by my customer, and just sent to me for re-gauging to EM gauge and repainting.
No.509 "Prince Albert" is a Great Central Railway 11F, or 'Improved Director' Class 4-4-0 (LNER Class D11 after the Grouping in 1923). This is basically a Bachmann model which has been converted to EM gauge with the use of an Alan Gibson conversion kit, then renumbered / renamed using bespoke plates from Guilplates.