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Based on pictures I found online, that appears to be out of a 1970's era Motorola car telephone.? There may be tuning instructions in the service manual but finding a 40+ year old manual could be a challenge.

A couple further thoughts.?
The factory TX and RX markings are from the perspective of a mobile that transmits in the 459 range and receives in the 454 range.
Sweep it to see where it's currently tuned.? That's what you should see if it's unmolested.
Also, this duplexer may only have about 60 dB of isolation because the carphone receiver had a Motrac helical filter to add isolation.
Unlike a typical flat-pack duplexer that is designed for high isolation on a single frequency pair, the carphone operated on a range of frequencies.
Those extra adjustments could be for optimizing flatness across the band.

Thanks for the info! I was able to find the tuning procedure here? in the message archives and, combined with your insights, it all makes sense now. The extra adjustments are capacitors to maximize the PASS characteristics of the transmit channel. I think it will still work for my purpose even with the low isolation since I'm only planning to use a couple of watts out.

IIRC these are three resonators on one side, and one on the other. The additional adjustments were loading caps that largely effected insertion loss on the RX path.? It's been 20 years since I fussed with one.? I've cut a number up to make specialized notches, and in one case to make a 2X2 5 W duplexer for an HT600 based balloon repeater. It was the only aluminum duplexer I could find, and weight was a major consideration.
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Oz (in DFW) N1OZ