As I see it any gun which pushes the ejectors in on closing by the breech face could likewise be termed as an assisted opener. Nothing at all rare about that as this is I believe the most common method of cocking ejectors. This could thus be called rare only if the particular model of gun was rarely fitted with ejectors.
As the vast majority of the US built Lefever Arms Co guns used inframe ejectors which do not push the ejectors in by the breech with only a few of the early guns have forend ejectors then this could be considered rare on them.
