It's very easy Ole. The obverse legend of KM# 25 is TRINIDAD AND TOBAGO while the obverse legend of KM# 29 is REPUBLIC OF TRINIDAD AND TOBAGO, so your coin is KM# 25.
It's a bit strange that the 1976 KM# 25 and 29 have the exact same mintage (although there's no mintage for the 1976 KM# 29 in Krause).
Quote: "Sjoelund"Where is the mint mark if present?
For coins from Trinidad & Tobago it's always on the obverse in the middle under the coat of arms except for the 1 dollar, 2 and 5 dollars 1972 where it's under the date.