Searching images for jerk injection pumps is likely to show at least a similar pump.
Re Howards comment on cleanliness – it is recommended to rebuild while immersed in clean fuel, to minimise any risk of introducing ‘scratchy’ particles during this process.
I expect fuel delivery is varied by shimming, to alter the pump stroke? Or was that timing? It’s ten years, or more since I took a Bryce pump apart. The usual problem, with these pumps, is the non-return valve on the delivery outlet to the pump.