Looking through my copy of a 1930 Jeffery catalog, I came across their page dedicated to the Jeffery's .600 Bore.

The text reads, " We recommend the Under Lever Push forward Snap Action, as shown in this illustration, for all powerful Smokeless Powder Rifles." I have been aware of this representation by Jeffery for some time, but have never understood what they were talking about.

There is a German action, called the "System Roux", which appears to be identical to the top lever double underlug actions, except that it is activeated by an under lever rather than a top lever.

If this is the case with the Jeffery, then why should they write "It is a far stronger Mechanism than the Top Lever, and it admits of nearly ten times as much pressure being applied to withdraw the bolt as can be got from a Top Lever" and "The cocking, opening of the Breech, and ejecting of the fired cartridge cases are much easier with the Under Lever Snap Action than with the Top Lever."? I can't see why cocking, opening the breech or ejection should have anything to do with the location of the actuating lever, unless actuating the underlever cocks the hammers in addition to unlocking the breech.

The price, incidentally, was 110 Pounds. (Which translates to about $9939, allowing for exchange rate and inflation. Pretty good buy!)