Same here... Last summer I looked with very bright LED flashlight and couldn't see markings on any of the isolators. I thought for sure I was included in the SB because my 12 is sn 58. Van's sent new isolators right away and I supported engine and loosened the two top mounts only to discover markings hidden by engine mount rings.
PPL/ASEL 1970 Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 317
LSRM-A Certificate 2016