Macgregor irons of varying length

Hi guys,
I am new to golf. I've got a very old set of Macgregor irons. I just realised that the length of the shafts get shorter by the number.
3 iron has the longest shaft while 9 iron has the shortest. Is this a normal setup? Please advise.

Each iron should normally be different by 0.5".

Yes. The bigger the number, the shorter the shaft.

thanks for your valuable advices!