There's a really odd Ambassadeur 5000 out there with internals that I have never seen and no idea what they're for! Perhaps some sort of 2-speed mechanism? No indication of that on the plates, they're standard 5000 plates. Just curious...
What's the number on the reel foot? That's very different, never saw anything like it. I'm wondering if it's an earlier 2 speed as the newer ones have the 2 speed gears on the brake plate.
wow! That's different.
That looks similar the levelwind gear plate you'd see on a 4600CB (part#12125 or 975035). The purpose of it is to disengage the line guide once it hits center of the frame during the cast. There's some sort of clutch built into it to accomplish that. That part is uncommon enough that I've never had the balls to destroy one just to see where its at lol.
If you remove the palmside plate of the reel, the system will get out of sync, so you'll have to reset it. First you'll center the line guide in the frame. Then you'll spin the gears in that plate the direction they spin during a cast. It should eventually lock. Once that happens, place the gear assembly back onto the frame and install the palmside plate. If you did it right, the line guide will stop in the center of the frame during a cast.
This one is a bit different from the stock one though, so I'd suspect it was an aftermarket part or was engineered together by someone. I've also never seen one in a 5000 class reel. On a wide framed reel, I feel like it would make backlashes more likely.