Forget the weight, that's got nothing to do with it.
Bit of a confusing question - SP14 is only the stylus, and its the cartridge that fits onto the arm...
I'll confess I don't know the exact names of the different arms on the Beogram 1000, I'm just aware that the older ones have a curved finger lift, later ones have a straight finger lift, and even later ones have a deeper cartridge socket by about 1mm. Whatever... The SP14 is a later stylus and will need a later cartridge and a later arm. The later cartridge doesn't have a noticeable rim around the base - everything is nice and flush. The later arm will be found on the likes of the Beogram 1001, and the Beogram 1000 that looks like a 1001.
If you try to fit the later cartridge onto an earlier arm, it will go on but there will be an embarrassing 1mm gap between the cartridge and the socket - doesn't stop it working, but it won't look right. If you try to fit an earlier cartridge onto a later arm it'll plug on fine and work fine, but won't be gripped as well (not that it'll matter.)
So... I'd guess the person who bought the stylus thought they were getting a stylus and cartridge.
Cheers, Steve