I'm currently restoring three 102's. Two are of the "S" variety. They have a pre-attenuator sample port on the front. If you look at the back of any -102, you will see two holes in the sub-chassis where the probe banana jacks are mounted. It's not difficult to add them to any -102. There is no cathode follower or buffer for the change. It will drag your frequency a bit, but you'll be using a frequency counter anyway when using the generator, so it doesn't really matter.
One of my 102's had an intermittent issue. It had no output unless I put side pressure on the main tuning capacitor knob. Clearly there was a bad solder joint, but visual inspection could not find it. I reheated every joint near the capacitor and bam, back to life and good as new. Whomever calibrated this one did an amazing job. It's super close at 455 and many other local haunts. Sweet.
So far, all the tubes are Mullard. Nice! I looked into buying a 12AT7. Gulp. Unreal expensive. Audiophiles are driving up all the prices?