So I was curious too and found a good resource for you (I think). Firstly, they do mention that since it is a copper pan you are talking about you may not want to re-tin it in certain cases:
In the case of copper, the tin prevents reaction with acidic foods. If you're not cooking acidic foods, then it's not necessary to have a tin lining. Also, if the copper pot is going to be subjected to very high temperatures, such as for making hard candy, the copper needs to be bare in order to support the high temperatures. And bare copper is desirable in making meringues, because of its reaction to egg whites, which makes them peak faster and longer.
- The previously quoted paragraph was found here
So yes, they are still safe to cook with, it seems.
However, if you want to re-tin them then you could use this form and send your pans to Fantes.com (based out of PA) to get your pans re-tinned. The cost is variable but here is how you calculate it:
- Measure each pan's width and height then add those 2 numbers together and divide by 2 for each pan you want re-tinned. that gives you the total inches (according to fantes).
- The cost per inch is $4 so multiply 4 by each inch.
- shipping is $10 for the first pan + lid, then $5 per each next one (pan or lid, i believe)
- Lids are to be measured and counted separately i believe.
There might be cheaper places out there, some additional searching could be done.