Interface: Quadrature
Old trackball made by unknown manufacturer in Taiwan. Unfortunately no any identification information is present on external labels or PCB. Looks like '90 era device.
Mechanics is a classic 2-shafts / 5-bearing one, but two out of 5 ball bearings are replaced with simple plastic bushings: apparently to reduce the cost. Main bearings are 693ZZ, and support one is R2: interesting mix of metric & imperial standards. Sensors are mechanical: contacts directly read conductive pattern on encoder disc. Formerly that design was used in early mice: I had once ancient Genius serial mouse using them. Now it's still widely used in many mouse wheel encoders. Switches are high-quality Matsushita AH1460. Connector is MiniDIN-9, formerly often used for "bus mouse" interface cards. Calculated resolution is 320 PPR / 58 CPI.
Overall design seems to be a clone of Asher Engineering Lynx/Turbo LX-200 (also mechanical by the way), but with slightly bigger & easily removable ball:
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Device is quite convenient to operate, but excessive rolling resistance due to friction in the encoders makes very unusual feel. Needless to say, it also prevents free spinning despite of relatively good mechanics. To make it usable, I've modded it into modern USB device. Fortunately, main bearings are of serviceable type (removable side shields), and support one is open type - so, it was easy to clean and re-lubricate them. Of course, I've replaced plastic "substitutions" back to the same type ball bearings, and polished the shafts. After that, movement of the ball become quite good: in line with classic samples from CH Products, ITAC or Disc Instrument.
Sensors were replaced with optical ones: I've used old Logitech M-S48 mouse as a donor for the shutter discs, quadrature sensors and controller. After addition of PS/2-USB converter, the trackball become common HID device with 578 PPR / 105 CPI resolution, very handy to use on modern systems.
Movement feel is amazing, as with any good ball bearings based trackball; the click feel is nice, too. As usually, the device was used to prepare & publish this article.