Any idea what percentage of your blocks had a coinbase signature? Or maybe you have a list of generation addresses? I could at least get a history of the blocks for a list of generation addresses, even if I couldn't get the shares per block.
When we switched to poolserverj from pushpool, which was using a new address for each block. Poolserverj used a static address which we changed from time to time, then shortly after we started using coinbase signatures
Search in this thread to find a date for it.