I know this is an old thread, but it was bugging me too that I couldn't remember what show this was, that my searching for it brought me to your thread.
So as I had nothing better to do this evening, I've just spent a good hour going through lists of old TV shows, and was about to give up, but then found it!
It's "Professor Poopsnagle's Steam Zeppelin".
To quote from Wikipedia "The golden salamanders had been buried long ago to indicate where each mineral could be found. After the first one was found, the cryptogram on it would lead the children and the doctor to the next one. What they had to do in each case was to decipher the cryptogram on each salamander."
Now just to find somewhere that streams the episodes!