L42A1 Transit Chest Markings Help

[Roy W]

1 Irish Guards ( the T is probably an I) = 1st Battalion Irish Guards
GDSM = Guardsman - a rank - private soldier
Kincaid = his surname/family name
12 = Could be anything, perhaps L42 number 12 in the Armoury

1 COY = 1st Company

2CG = 2nd Battalion Coldstream Guards. (obviously the rifle moved between regiments at some point)
1 COY = 1 st Company

LONDON/74 = London District (where they were based when they had the rifle. 74 is probably the numerical code for London District)