The supplementary Interurban cars had a very complex history, partly due to the Granville accident.
They were marshalled originally in eight car sets.
The third digit of the number indicated the set:
So 2700 to 2707 formed set 10
And 2710 to 2717 formed set 11
Each set was divided into four smaller sets, so 10a, 10b, 10c, 10d each with one car with guard's compartment (MFH)
The set numbers were painted on the outer end of the MFH and remained there for years after the set idea went away.
I think all the (original) cars in sets 10 and 11 retained the 3AG bogies.
It is possible that most later cars had the cast 2CA type....
So the MFH models with L7 logos should probably have set numbers, if their third number was 0 or 1
As indicated above, after Granville there was some hasty remunbering (I don't think set 11 was in service by then).
Things continued to be confusing after the idea of sets was given up.
Cars with fourth digits above 7 were built eg 2708.
The last few cars arrived in SRA bright red (candy) and with aluminium framed windows.
Other cars were painted in SRA bright red.
But for 1988, many cars in SRA bright red were repainted Indian Red to run on heritage trains fot the Bicentenary, including at least one car with Beclawat windows that had never been indian red in that form before.
I tried to photograph both sides of each car of those on the two trains for the blessing of the bells in Goulburn.
Each train had a Bicentennial 81 class, and 3801 led one train south and the other north.
Most of the supplementary interurban cars were on these two trains (including one IFS and one MFS).