Design of Euro 30 and Euro 50 changed around 2013.

Euro 30 uses the same seals and orings as before.
Euro 50 has different seal and orings

Here are photos that help to identify the new design. The most obvious difference is the plate that goes directly behind the impeller.
In old design, it is flat on both sides.
On newest design, it has a cup welded to it on the backside.
First photo shows this plate with part of seal installed.
Second photo shows exposed motor shaft before assembling.
Third photo. put other part of seal on shaft as shown---spring toward inside
Place the flat plate (with other part of seal installed as in photo) with cup/seal facing inward. be sure to use small oring as well.
then the impeller, orings, pumphead.