I played the original back in 1993 on my Amiga500 and finished it... NOT. Because the Amiga version has a bug that won't let you finish the game even if you control 101% of the necessary towns. Very frustrating. Later I finished it on the PC.
I have played the game for a total of about 10000 days and can tell you this:
I never found a mine detector.
I did find radio parts, but never all of them in the same game.
A repaired item is worth more than its parts, so the repaired radio might actually just be for trading.
Offering items at the bar does give you a hint on its value, however ROUNDED DOWN! For example, a rat is worth 3 DR, whereas 2 rats are worth 7 DR if I remember correctly. There are quite a few items which are worth "x.5" rations.
As soon as I can afford it, I travel with a companion. I usually take a mechanic along, because that way I can build anything wherever I am and only need to hire one in the whole game.
AFAIK, the computer-controlled opponents CHEAT in the PC version. On the Amiga you have absolutely no problems killing them, they die almost the first time you trap them between two towns.
If your food stack in a town is full, just fill the guard's inventory. If it's full again, switch the produced type of food in the INFO-screen.
Sometimes I make a habit of buying an empty water sack, fill it, and sell it for another empty water sack and something else, as the difference is greater than the margin of the trader. Or I hoard them, as sometimes a trader seems to have an endless supply that refills his stock every day, and then I go shopping with a truckload of full water sacks.
k:
But thanks, there are a few things I never discovered, like armor from clothing (I assumed, since I can't use pulllovers etc, that they are only for barter) and use of ropes to reach some places (honestly, I thought the coders messed up some towns and forgot to make paths to the caves).
It's a classic, it's great, and it need's a multiplayer (4+) network option!
Claudio