QG, I'm aware that at least one version of Voigtlaender's Ultron (IIRC, might have been a Septon) has a front element that's concave outwards. This configuration is very uncommon. It appears -- the sketch might not be quite correct -- that the monster's outer meniscii will fit facing either direction; convex or concave outwards.

There are a fair number of double Gauss variants with the outer meniscus split. I just took a quick look in the VM and a couple of Soviet sources, found a number of such lenses, none with the outer element(s) concave outwards.

It could well be assembled properly, but it doesn't have to be.