I missed the fact that there was no time interval involved after the battery was installed and the voltage was reading 10.6V.

Therefore, the advice given by WHunter in the above post should be followed first.

You don't have a small current leak. You either have a bad battery or a dead short, as mentioned above.

The remaining possibility is terminal clamps that are in poor condition. Did you take the voltage measurement directly on the battery posts or on the cable clamps? It's possible to have a slight voltage drop across the clamps, but the clamps would need to be in very bad conditon for this to occur with low load.