Sorry I did not clarify the terms.
A folding shotgun is a break open action where the barrel is attached to the action via a screw-in cross pin. Normally it cannot be taken down like a "normal" break open shotgun by taking off the forend. The gun can fold over on itself rather than be taken down. In the UK the type is often called a "poacher's gun" due to its foldability and resulting concealability.
The Beretta 412 SB, the Bernardelli Game SXS, Investarm OUs, are typical modern folding guns. Prewar folding shotguns were offered by many Spanish and Belgian makers, both single and SXS.
The typical folding shotgun does not have separate lumps, no middle bridge in the action, no supporting steel in front of the cross pin. In other words it is missing the parts that are often cited as being important if not vital to action strength.
