All the lower pins are identical(fwd,LH and RH). The upper pins are a larger diameter and longer than the lower pins. They look very different. The lower pin has 2 flats on the head of the pin and the upper pins have 2 flats on a shoulder which protrudes from the head. The flats are there so you can rotate the pin to insert the nappy pins x2 in an acceptable position where they won't foul on anything.
You would only be able to mistakenly fit a lower pin in the upper (lift housing) holes! Not the other way around! It is unlikely any 225 engineer would not notice this on install or during subsequent after last flight inspections.