Best accessory rangefinder?

I've got a 4.5x6 Ikonta with Tessar lens on its way and would like to get a rangefinder accessory for it.

What makes are good to go for? I'm looking for something that can be recalibrated easy enough, preferably by me and has a proven track record for reliability.

Are there any star/dogs to seek/avoid?

Have a Telex (german) rangefinder. AllI can say it works. Should be pretty easy to find one.

I have a few all work OK, make sure that the scale is the same as the camera, feet or meters. Zeiss used the appropriate scale for the market the camera was sold in.

Ian

I have a Voigtlander one I've had since 1959 that's easy to adjust and is calibrated in feet .