Measured antenna tuning an it is quite a bit off unfortunately, see screenshot. Antenna dips at 1055MHz not at 1090 (so it could be quite a bit better!) Did however increased my range quite a bit (combined with active amplifier with 1090 filter) so I'll keep it for now.
Very high quality. Well made. Looks like it is sealed well. I might have put some extra sealant around the connector to really make it water and dust-proof, but I can do that myself. Now let's just hope it works as well as it looks.