Marsland, if I remember correctly, basically took LR's setup for doing Series chassis and started making them, basically to spec, but by far and large, they galvanize them (why go through the work of doing a swap on one that isn't galvanized?). Marsland's chassis are all SIII ones, I think; they work for a II/IIa, but there are some variances. I've developed the impression that while they have a higher volume than the others, Marsland maintains a high quality, have never heard of issue w/ one.
Richards, I believe, produces fewer in volume, but will do more-specific chassis.... if you want a late SI chassis, or specifically a SII chassis and not a SIII chassis, they can do it. No idea on quality.
FWIW......