seal (或 stamp) of approval

an official statement or indication that something is accepted or regarded favourably

正式批準(zhǔn)

on approval

For examination or trial by a customer without the obligation to buy

試穿：為顧客作檢查和試穿的，沒(méi)有義務(wù)購(gòu)買

took the dress on approval.

試穿裙子