(I have an STI Spartan which uses the same LPA adjustable rear}
STI Spartans, at least the earlier one's, were made in the Phillipines by Armscor and didnt use an actual LPA rear sight. They used a Phillipino made copy of it. The reason I asked about replacing the rear sight is that the same gun is available from the factory with fixed sights and is cheaper so... ?
LPA's are a decent sight but are not top of the line copies, there are better available. The Harrison replacement fixed sight is ok but a bit bulky for my tastes, I much prefer the Hiene Slant Pro.