Working on AZAM 1967 with 4.5 mm pipes Dot 4 and discovered a green marked seal, maybe LHM. If the seal is meant for LHM it would mean that Dot 4 doesn't dissolve the rubber? Anyone seen this before?

defo a LHM seal

Although Id not have expected a seal to have "dissolved" it does look pretty messy, most lhm seals in LHM systems you look at and think "oh I'd happily re use that" there is no way you'd ever think that of that seal.

The mixing of the wrong seal usually causes embrittlement or swelling which might not be obvious on pipe seals but could be catastrophic in calipers or pistons

I'd certainly not look at that and think its ok to mix the seals in the system, especially if it was for someone else’s car.

Viking,
using the wrong seal/brake fluid combination results in damage to the seals, rather than them being 'dissolved'.
The result in both cases is that the master cylinder, calipers or 'wheel' cylinders are rendered useless.

I've had to repair far too many A series brake systems which had been dosed with the wrong fluid, usually it's synthetic brake fluid into an LHM system but LHM into a drum brake system is just as bad.

ken