951 piston inquiry

[nikko_m]

i have a pair of mint pistons given by a friend,he told me its for a 951 carb engine,now the problem is that he forgot already what brand are the pistons,it only has these markings on top 87.88 and 2374.02 and inside the skirt is ASSO-W.so its not prox,wiseco,sbt and wsm.so i am wondering who made these pistons.maybe you guys encountered those markings.thanks