I have some experience with interfacing with AMC PCB-mount boards in this fashion: https://www.a-m-c.com/products/?_form_factor=pcb-mount https://www.a-m-c.com/

I have some experience with interfacing with AMC PCB-mount boards in this fashion: https://www.a-m-c.com/products/?_form_factor=pcb-mount https://www.a-m-c.com/products/?_form_factor=pcb-mount I don't hate the style of pin headers they're using. Probably considered laughably low density by modern standards, but for industrial stuff they're robust. Never had issue with alignment, but they are not keyed, so it could happen I guess. For modern, high-speed, high-density you could look into Samtec board-to-board offerings: https://www.samtec.com/connectors/high-speed-board-to-board https://www.samtec.com/connectors/high-speed-board-to-board though the big names (Molex, TE, etc) probably have equivalent stuff.