In 1950, Kern-Paillard introduced a new line of lenses with a unique depth of field scale, termed "Visifocus". The Visifocus system consisted of a curved scale, indicated by a series of orange colored dots that appeared or disappeared when the diaphragm scale was stopped up or down. The dots provided a visual reference of the depth of field for different focus settings at each f-stop.
Further innovations were made in 1956 with the introduction of the Bolex H-16 Reflex camera. The camera used a beam-splitting prism system to provide reflex viewing by diverting approximately 25% of the light entering the lens into the viewfinder. Although the H-16 Reflex used a standard C mount, the reflex prism (located behind the lens and in front of the film plane) affected the optical correction of lenses of 50mm focal lengths and shorter. Kern-Paillard introduced a line of "RX" mount lenses which were optically corrected for the Reflex camera.
During the 1950s, Paillard adopted product codes for accessories and lenses. These were used to identify items for sales, repair and service purposes and seems to have been done away with by the early 60s. For the sake of historical reference, I've listed them below. Many of the same lenses were available in both standard (listed as "St." for all 16mm C mount cameras) and RX mount (For H-16 reflex cameras) and used different product codes. Apart from the letters "RX" appearing on some, they were otherwise identical in appearance.
D Mount Lenses for 8mm Cameras
Switar 5.5mm f/1.8 (SWINQ)
Wide angle lens, introduced in 1954.
Pizar 5.5mm f/2 (also f/1.9) (PIZUI)
Wide angle lens with fixed focus and a maximum aperture of f/2; introduced in 1957. A later version was available in 1959; it had a maximum aperture of f/1.9. Both were fixed focus lenses and were identical in appearance.
Switar 12.5mm f/1.9 (SWIHO)
Standard focal length lens with an engraved depth of field scale.
Yvar 12.5mm f/2.5 (FICIN)
A standard focal length lens; fixed focus.
Yvar 12.5mm f/2.5 (BECIN)
Standard focal length lens with a focusing ring and engraved depth of field scale.
Yvar Filtin 12.5mm f/2.8 (FILTI)
This lens was introduced in 1954 and contained four (4) built in filters; yellow, red, "daylight" and "skylight". Filters could be selected by turning a knurled index ring. Four "no filter" positions were marked between each filter position. The Filtin could focus from 1 1/2 feet to infinity and close down to f/22.
Switar 13mm f/0.9 Visifocus
A very fast lens of standard focal length, introduced in 1959.
Yvar 13mm f/1.8 Visifocus
This standard focal length lens, introduced in 1959, used the Visifocus depth of field scale.
Yvar 13mm f/1.9 Visifocus (HUVAR)
A standard focal length lens, with focusing ring and Visifocus depth of field scale.
Yvar 13mm f/1.9 Fix-Focus
A fixed focus, standard focal length lens.
Yvar 25mm f/2.5 Visifocus (HUARO)
Standard focal length lens; Visifocus scale.
Switar 36mm f/1.8 Visifocus
A fast telephoto lens, introduced in 1959. It came with a detachable lens hood.
Yvar 36mm f/2.8 Visifocus (YVITA)
Telephoto lens with a Visifocus DOF scale.
C and RX Mount Lenses for H-16 Cameras
Switar 10mm f/1.6 (st. SWEDI, RX DAADI)
These wide angle lenses were introduced in 1956. Two versions were available; in standard C mount for non-reflex cameras (SWEDI) and in RX mount for the H-16 Reflex (DAADI).
Switar 16mm f/1.8 (st. SWESE, RX DAESE)
This Visifocus lens was introduced in 1954, with a standard C mount (SWESE); a RX mount version (DAESE) was available in 1956.
Yvar 16mm f/2.8 (st. YVERI)
A moderately wide angle lens with Visifocus scale; normal C Mount.
Switar 25mm f/1.4 (st. SWITA, RX DAITA)
This standard focal length lens was first manufactured in the 1940s, but production continued until the late '50s, approximately. It used a standard "compass-style" depth of field scale. A RX mount version was available in 1956, for H-16 reflex cameras.
Switar 25mm f/1.5 Visifocus
A standard focal length lens with a Visifocus depth of field scale; for non reflex 16mm cameras with a standard c-mount.
Pizar 25mm f/1.5 RX
Standard focal length lens with Visifocus DOF scale, introduced in 1957; in "RX mount" for H-16 reflex cameras.
Yvar 25mm f/1.8 Visifocus
This lens appears to have been introduced in 1958 or 1959. It was only available in standard C mount, and priced the lowest among standard focal length lenses.
Pizar 26mm f/1.9 Visifocus (HAPIZ)
Standard focal length lens, for use with non-reflex 16mm cameras; normal c-mount, with a visifocus depth of field scale
Switar 50mm f/1.4 (St. SWIFI, RX DAIFI)
A telephoto lens that was available in both standard c-mount and "RX" mount; the standard version (SWIFI) was introduced in 1954, while the RX mount version (DAIFI) was introduced in 1956. It came with a detachable lens shade.
Pizar 50mm f/1.8 Visifocus (St. and RX versions)
Introduced in the late 1959, this telephoto lens was available in both C mount and RX mount; both with a Visifocus DOF scale.
Switar 75mm f/1.9 (DAORA)
Standard C mount; fast telephoto lens. It came with a detachable lens shade.
Yvar 75mm f/2.8 (YVORA)
Telephoto lens with Visifocus DOF scale, introduced in 1950; a detachable lens shade and leather case was included. This lens could be mounted on the turret with any compliment of shorter focal length lenses without obstructing the field of view.
Yvar 100mm f/3.3 (YVENT)
Telephoto lens with 4x magnification compared to a standard 25mm focal length lens; visifocus depth of field scale. Introduced in 1950. It came with a detachable lens shade and leather case. With its length of 6 1/2", it was recommended only as an accessory lens as it would obstruct the field of view of shorter focal length lenses.
Yvar 150mm f/4 (YVONG)
Extreme telephoto lens, approximately 7 1/2 inches in length with a weight of 7.5 ounces. It was introduced in 1950 and came complete with a leather carrying case and shoulder strap. A detachable lens shade was also included. Because of its over-all length, it was recommended only as an accessory lens and not intended to be mounted with lenses of shorter focal lengths.