I'm sorry to resurrect an old thread, but I just received the same form SSA-L99-C1 in the mail this week. For me, the year reported was 1993. The old employer listed and the firm handling their pension and retirement accounts, Fidelity, have no account information for me.
My merger history is very similar to what I quoted below (might have been the same companies!), so it is very possible my few pension credits with Company A made its way to Company C. Very disconcerting that I have no idea why Company A reported the information in 1993 (the year of the Company AB merger). I have sent a secure message to my last employer in the merger line, Company C, documenting that information. We'll see what they say.
Moderators: If I shouldn't have bumped up this thread, please delete mine. Much of what I would likely hear is already stated on this thread.