Using service number allocations given at
I am trying to determine enlistment dates and locations for the crew of Halifax HR732 MH-Y

Four with 7 digit numbers make sense, one RCAF would not apply, and the following two with 6 digit numbers don't make sense to me (both English) as they map to 155001 to 160000 Oct 1917-Dec 1918 RFC/RAF - civilians (Boys)??

156123 Arthur Jack Salvage (age 23 when KIA)
156607 Fredrick John Baker (age 21 when KIA)

I would expect they enlisted 1940 to mid 41