Never say never with LE's but I'm fairly sure that Maltby's we never issued with steel butt-plates, Brass, yes.
As far as I remember the steel butt plates were a temporary 'fix' for Long Branch (Canadianrifles)
The other material used (primarily by Savage and Long Branch) was the 'pot-metal' known by various names Mazac, zamacor Zamak
(ZAMAC is an acronym for the Zinc, Aluminum, Magnesium, and Copper alloy that Hot Wheels, Dinky and other pre-WW2 die-cast toy cars are cast from).