The reason that we can't find Heuers in this period is that Heuer produced few pieces.
If we tell that there are 1000 Siffert produced between spring of 1969 and the end of 1972, how many watches gone destroyed, drowned, disassembled for spare parts?
In this 10 years a lot of watchmaker put together what remain of these watches.

Now parts are almost ended... I think that we've to hold our watches: it's muche better than give money to the banks (and be shure to loose them...).

In Italy vintage watches dealers hate Heuer because a lot of people want to buy Autavia, Monaco, carrera and other models but they can't find good pieces on the market.
And they discourage customers to buy an Heuer for the poor movements or poor dials!
Sometimes, when they find an Heuer, they put on the market at fool price and they are also able to sell at these prices!