Lee, very interesting information. I'd never thought about the possibility of reversing the polarity of a lead-acid battery, but there is no reason it can't happen. I had to go back to my old chemistry texts to refresh my memory of the details of the process.
When fully discharged, the "positive" and "negative" plates are actually lead sulphate (PbSO4) and the electrolyte is mostly water. So, when charging occurs, electrons are forced from the positive plate which is converted from PbSO4 to PbO2, and the negative plate gains the electrons and is converted from PbSO4 to Pb (pure lead). And, the SO2 ions from this process create more sulphuric acid in the electrolyte, so the specific gravity (and acidity) increases.
Accordingly, when completely discharged, the battery doesn't care which plates are forced to be positive or negative. The polarity is established upon charging (assuming the battery is COMPLETELY discharged prior to charging).
Neat information. Thanks for the insight.