Thanks Gomiville. I like both versions. Do you think commercial or primitive armor would be more common?
I think they're probably both equally common, on low-tech worlds.
I always imagine commercial armor as thick steel. It's tech level B, which is WWI-ish, just cheap component materials, layered on. Very simple and cheap to make, but not really proof against "modern" weapons. (Commercial armor on a high-tech world might use a different material than just simple steel, but the mass and protection are equivalent.)
Primitive/Industrial armor is fancier laminate armor or something. Tech level C, mid- to late-20th century tech, so I imagine a 1970's era tank or something. Also pretty simple to make, and proof against modern weapons, but heavy and inefficient.
In my mind, the commercial armor is something a tractor factory could produce, like simple IC engines and rockets. Primitive/industrial armor is more intentionally military (unless you're a high-tech planet), similar to many Tech C weapons (standard ACs, standard missile systems, etc). So, a low-tech world could produce both pretty easily, provided it has a military industry. If it's a bunch of farmers arming up for revolt, I might stick with the commercial armor, but otherwise, it's a matter of flavor. (For example, a tank might use primitive armor, but a cheap APC might use commercial armor, contracting the production out to the aforementioned tractor factories.)
I have a love for low-tech BT systems, so I've probably spent too much time dwelling on this kind of thing.