Do you mean they won't work if you mix them up?
This is, apparently, a VxMR:
This other one an N111HE:
The shade of red doesn't seem to be the same - mine looks more like the first one, that red wine-ish tint. Also, looking at them - mine has the raised 'pip' at the front of the brush assembly, the white marker to aid cueing. The bottom one has a sunken-in mark instead.
It doesn't really make a difference, having said that - the stylus is what sets them apart, I'd think, and it's broken off. But the brush works well enough, and it was free so...
I just spent the whole evening listening to records, hadn't done that in a while, it just kept asking for more.
Edit: also, there's no logical reason anyone would mount a cartridge using Superglue and yet this one was all caked in it... so I don't think we can trust the previous owner too much

.