Final answer:
A deputy or agent would enter a US Treasury check cashed on Line 7.3 of the DD Form 2665.
Step-by-step explanation:
On the DD Form 2665, which is used for daily accounting of financial transactions by cashiers within the Department of Defense, a deputy or agent would enter a US Treasury check cashed on Line 7.3. The form is utilized by cashiers to record various financial transactions, including the cashing of treasury checks. Properly recording transactions on the appropriate lines ensures accuracy in reporting and accountability of funds.