LVM: "Optimus Quick Acting Portrait f4.0 This was made in 1B, 4.5in for CDV; 2B 5.75in for Cabinet; and 3B 9.0in for Grand Cabinet, the last name suggesting these may just be from a French source. Note that in 1889 only 1B, 2B and 3B were listed but larger sizes were to order"
Optimus was a name used for more Perkin lenses, this was the only one listed with an F-stop of f4. Maybe someone else can tell more about the lens design and what it may resemble.