We see a few Merkels in the UK, but very few Simpsons, which I have only seen in the 'boxlock' versions.
The Merkel name has the 303E (top of model range) sidelock which has both Kerstens and underbolts, and a neatly 'hidden' catch for the hand detachable locks.
The 203E - is a simpler sidelock with only the Kerstens, simpler ejectors and 'visible' release for the locks.
Both single and double trigger versions are seen (double trigger o/u guns are not very common in the UK). On all I have owned (3), the triggers have been poor, being set very heavy. They have benefited greatly from proper adjustment by a skilled gunsmith, after which they have been good. It may be coincidence, but two of mine have suffered lifted ribs which has needed attention.
