Use "London Pattern Pulley" (or LPP) to search for an image. For my purposes, take two elongated diamond shaped plates. Draw a line from the diamond points to find center and locate a pulley sheave there, sandwichd between the plates. Drill holes in the ends furthest from center to accept through bolts for D-rings/chokers, etc. creating the LPP snatch block. The idea is that this snatch block can be attached in a line of pull while still leaving the pulley free to be used.
The application I have in mind is a 3:1 where the LPP snatch block is hooked to the item to be pulled (lets call it a stump) with a choker. Attach the pulling cable to the other end of the LPP snatch block, then run the pulling cable through another snatch block that is secured to an anchor. Now run the pulling cable back to the LPP snatch blocks pulley and finally to the winch/tractor. This eliminates having to otherwise use two chokers/chains on the stump being pulled.
The only working version of this LPP style snatch block I have seen was on YouTube and it was machine shop fabricated from plate steel. The genuine London Pattern Pulleys I have found images of all have a swivel mounted eye on one end and either a through hole or a D-ring on the other. The eye on-a-swivel looks weak. Not to mention it'd have to come from the UK.