I began to knit in the heyday of machine knitting, when local, national, and international seminars were held with accompanying marketplaces that made imported magazines and tools available directly from factories in Japan and Europe. As a result, I accumulated a huge stash of tools, including those for the Passap models, which also included duplicates of the Japanese tools with 5mm spacings.
I no longer own my Passap equipment.
My present shares address 4.5 and 9mm tools. Of those pictured below,
most were easily and commonly found, except for the accessory at the upper right and the gadget that accompanied the one on the bottom right (which I do not own). 
A few more:
Some have been frequently used, others were handy in demos, and a few have been waiting to meet machines or knits.
My remaining stash of 9mm tools is not pictured; that said, several pairs of now hard-to-find tools marked MT Stitch Tender are among them. 
Both German and Japanese manufacturers, at one point, provided an accessory to help in manual needle selection in patterns. Some were called Jac-40s, and the Brother model immediately became rare.
Adding to the confusion in terms of branding is that Knittax and the all-metal German-made KnitKing were closely related, effectively the same product marketed under different names in different regions during the 1950s and 1960s. Knittax was a 5mm machine.
The KnitKing name later became associated with Japanese plastic and metal Brother machines.
Some knitting machine history may be found in Daisyknits Brother compatibility charts and history, and Knitting machine history and information, Silver Reed +.
Information on the Passap Jac-40 and how to use it can be downloaded for free in two versions:
https://mkmanuals.com/downloadable/download/sample/sample_id/1001/
https://mkmanuals.com/downloadable/download/sample/sample_id/1002/
The Brother Jac is described as having been blue, 
while the Passaps were supplied in more than one color, sometimes marked with made in Germany. 
Early studio 9 mm metal beds came with no card reader or pattern selector.
My first machine was one, a Singer SK 150 metal bed. The PS 150 became available, a 12-stitch pattern selector that used punch cards as well, a collection of such card designs.
An excerpt from the PS manual: 
The first few pages of how to use the 9mm version pictured at the top right of the first photo begin to explain its potential use for manually selecting and knitting patterns, sometimes with changes required every single row.
Added images in More on Brother DBJ, including KR 260 bulky KM options.
As built-in card readers were added to machines, adjustable tools were modified, with some are still available to aid in hand selection of needles or pushers, ie, the Passap 30 count model for 5mm machines, 
and now, with the advent of 3D printing, a version for the file for a 4.5 mm version with 36 slots: https://www.thingiverse.com/thing:5252410,
the description by the designer; 16.5 cm long ruler with 36 spaces for removable needle pushers for a flat bed knitting machine. Can be used to create unique patterns with a 36-stitch repeat. Designed for a standard gauge knitting machine, the spaces are 4.5 mm apart. Works equally well on a 9 mm gauge bulky knitting machine, just omit every other space.
Accessories and tools can be a boon in repetitive needle selections on either bed when automatic pattern selection is not available or possible.
I do not own a 3D printer, but have been able to acquire the adjustable selector and a stitch ditcher-slider for use on my 4.5mm Brother machines; info on its use to follow in a separate blog post. 
The 3D printed 36 selector operates akin to the factory-manufactured ones discussed above.
On wider needle groups, if moving from left to right, match some of the selections on the left of the tool to those on the needle bed on the right, and continue to select from there.
Some literature refers to the small companion pieces as needle pushers, in eBay Passap listings as pusher teeth, and here they are referred to as pins.
Some tips: not consistently inserting the pins in the same direction leads to incorrect spacing, as seen in the two groups on the right. 
To avoid that, mark to identify the facing side, and insert pins consistently with the nub side up or down. Having additional color pins or tools can help with irregular needle selections. 
One possible use of the tool on the single/ knit bed is to use it to make repeated selections in short rows. Pins may be inserted for needle arrangements between opposite beds at custom intervals. For illustration, here the selections are fixed.
Placing the required number of pins on either side of the tool, the rest can be used as a handle to maneuver the pins to move stitches out to the hold position or push them back into the work position.
When working on both beds with the ribber pitch set on P:
pins need to be inserted consistently, ie, beginning with nubs up in the slots on the top and nubs down into the slots at the bottom. 
This was my test selection; 
there is consistent spacing between and touching of adjacent pins across both sides of the tool. 
When the ribber pitch is set to H, the spacing is altered between the groups on the top bed and those on the bottom, as seen on the left, requiring adjustments. 
The tool, used with the marked side up and with pins inserted with nubs facing down, toward the back of the marked side, resulted in the following selection. The single pin on the left serves as an aid in its placement.
Pins are so easily moved/ turned that custom placement can be tested to fulfill desired needle selection sequences.