What do the pins mean on this rotary encoder?

I'm trying to repair a speaker of mine (old AudioEngine A5). The encoder that controls the volume is not working properly and turning the volume up REALLY loud sometimes when you touch it.

I had some encoders lying around so thought I would try and replace it, but the newer encoder has one more pin and the names on it are very different.

Any idea what these pins mean, or alternatively where I could source the same encoder?

These are the pins on the broken encoder:

These are the pins on the new encoder:

Also, I've tried googling for the part number but nothing turns up. Am I looking at some different type of encoder maybe?

Here's a pic of the part numbers for the broken encoder: