Speedometer Help

[westbound]

Hi all, my speedo has not worked since I bought my 1975 SIII 109. Finally had some time to take the dash apart and investigate, and I found the cable and speedo are not matched. Basically I have what appears to be a SIII clip-on type cable, but the back of my speedo does not have a machine-notch to accept the plastic clip on the speedo cable - so the cable pulls right off the back of the speedo. I understand the SIII cables use a plastic clip, and the II/IIA cables had a threaded end on the cable. My speedo appears to not be set up to accept either cable type. My speedo is not threaded nor does it have the machined-notch to catch the plastic cable end from sliding off the speedo. It’s a jaeger gauge, SNT - 6209/07AS 880

I will post pics of everything, and I’m wondering do I have the wrong speedo cable, or the wrong speedo gauge? I took the gauge apart, cleaned everything, found a cracked 20-teeth gear which I plan to replace, but overall the speedo gauge works. I’ve been testing it with a drill and it works fine. The speedo cable also works as I’ve driven around town and watched the cable spin around as I drive.

I’m hoping I can replace the cable with the correct cable for this speedo. Rather spend $30 on a cable rather than $350 on a new speedo.

thanks!