I have seen a handful of post bases and they've all looked very similar to Jerry's picture above. It is not as pretty as the rest of the boat, but since this component works only under compression, it is built solidly enough. There is a teak block underneath the mess of glass as far as I've seen. I've cleaned-up C-155's a bit, but I decided to leave it alone as it is a hard area to work in unless you have the sole out - and I did not want to do that...
If you do some work in this area remember to provide drainage underneath or water will pool-up in the front... I've seen this too.