Not sure what you mean by "Off Market". All the Testnet Bitcoins on the exchange have been deposits by users.
I can add user deposit and withdrawal data as well in the next fix up, if thats what you meant.
"Off-market Transaction" is a commonly used phrase in Stock Market circles to indicate transfers / buy / sell that do not happen via an exchange like BSE / NSE. For e.g. Assume I have two trading and demat accounts, one with ICICIDirect and one with Kotak Securities, I can fill out a form called a TFID and transfer any shares from one account to the other. I can also do that for consideration and sell to another party. These transactions are called Off-Market Transactions.
Your description of 'deposits' and 'widthdrawals' match closely with above standard description of Off-market-transactions. Hope that made sense.