The proof Marks with that wording indicate a date between 1896 and 1904. There were several push forward underlever actions usually incorporating some form of action cocking or bringing the hammers back to half cock position. By the time your gun was made they were less in use. Ones to look at are Joseph Lang's patent, Gibb's patent and Edgar Harrison's patent. May have a few more ideas when pictures are shown. Lagopus.....