ABU 5000C, 6-digit numbers

I have many 5000Cs with a 6-digit number on the foot. As far as what I have in my collection, the logo of 'ABU SVANGSTA (the former A has an umlaut mark, to be exact)' is engraved on the left side. The later ones may have a beveled-head handle nut marked 'Oil', which is different from earlier ones with a round head. These models were supposed to be made until 1971 or 1972.