If no depreciation entry passed for the past ten years, then how come your B/S shows a balance in the Accummulated Depr. Account?

It depends on whether the failure to depreciate the asset was done in error (as in you forgot or were trying to manipulate earnings) or as a change in accounting estimate (as in you reassessed the assets and its salvage value and found that the asset had already been depreciated to its salvage value and no further depreciation was necessary).

If a case can be made that this was simply a change in estimate and there was some sort of reasoning for the lack of depreciation (the only one I can think of is that it has been depreciated down to its salvage value) then what I would do is either 1) nothing, take the gain/loss on sale or 2) reassess the asset in the current year, figure out what this year's depreciation should be based on its remaining useful life, and then take this years depreciation amount before you write it off the books. Then take the remaining gain/loss.

However, if you guys just forgot to depreciate, then this is an error and restatement needs to occur. Restate the earliest shown i/s in a comparable balance sheet and adjust the beginning retained earnings account for any effects of changes prior to the earliest shown i/s. (DR-RE and CR-AD)

Hope this helps!