Need advice on this device

My wife purchased at a garage sale a “Eagles Nest Boat Hoist”. Seems somewhat similar to Harken lifts but different enough that I can’t figure how to install it. The company seems to be gone and I’m not able to find a manual or instructions online. Didn’t come with instructions.

Is anyone familiar with this thing and able to give me insight about how to install it? I’d be grateful….

Thanks,
JP