Umm to start, does the Siltronix 90 have the numeral "3" rubber-stamped onto the rear panel?
If it's another numeral, not "3", you have a version meant for some other kind of radio. The "3" version feeds 16.27 MHz into the radio when the dial is set to channel 1. If you have a frequency counter with an input jack and a patch cord with the right ends on it, plug the output jack of the slider into your counter input. This permits you to verify that what's coming out of the slider will in fact match your Mark III.
I do hope your Browning transmitter is the Mark III SSB transmitter, in the same size cabinet as the receiver. The so-called "half" transmitters (like the one in my sig) are AM-only, and will not hook up to a slider directly without modification.
The good news is that the small, cheap (around $50) external displays used for Galaxy mobile radios will match the frequency setup in the slider on a Mark III SSB transmitter.
If you have ever used a Glenn slider with a Mark III SSB, you'll know that with the Glenn on "standby", the display will NOT read zero, but will show "10.695". Oddly enough, this is the same internal "offset" arithmetic built into the Galaxy external displays with the 6-pin plug on them. What we've been doing is to punch a hole in the slider's rear panel, just below the top edge. A rubber grommet goes in, and the 6-pin plug gets cut off the end of the display's cable, fed through the grommet. The red wire gets lap-spliced to the wire that fed the light bulb. You don't need that bulb any longer, and the counter consumes only a bit more juice than the bulb did. The display's black ground wire and the coax both go to the slider's circuit board, to tap off and feed into the display.
The adhesive-backed velcro that comes with the display will keep it in place atop the slider, like this.
If the internal 5 MHz crystals in the Mark III SSB transmitter have drifted, you might need to tweak the trimmer capacitor inside the display to make it read correctly.
Once you have gone to all this trouble, wiring the slider cable up to the channel selector in the Browning, and wire the display, you'll be disappointed to find that the transmitter always shows less power using the slider than when a crystal is selected. We have a solution to that problem, made to bolt right into the transmitter under the chassis. It boosts the slider's drive level so that it's the same as the crystals deliver.
Nomad Radio Slider Buffer
If you just hook up the Siltronix directly to the channel selector, you'll find the the
shorter the slider cable, the more power the transmitter gets when the slider is selected. The buffer eliminates this odd quirk, too.
The main reason to use the Galaxy display is that it reads full-time, while receiving AND transmitting. You can always use a general-purpose counter that goes in the antenna coax, with a jumper. This kind of counter won't care what kind or radio it's hooked to, but will read ONLY while you are keyed on AM, and when the modulation level is low enough, and NOT while receiving.
Now all you have to worry about is how much of all that 35 year-old stuff in the Browning is still good.
73