It sounds to me like the OP is interested in outing an acquaintance he suspects is a BS artist.
As others have said, the answer is “no”. Neither you nor the supposed BSer has any ability to back up or to debunk those claims with official records. At least not directly.
The DD-214 will list the jobs & ranks held. Which gives clues, but only if you already have the background knowledge of which jobs at which levels in which services in which era typically have what clearance.
Further, I’m not sure what use the info is. If somebody is saying “I used to have clearance X so I know supposedly secret factoid Y”, well he’s pretty well proved he didn’t have X & doesn’t know Y.
Your own knowledge never really becomes declassified. So when you leave the job the stuff in your head becomes “write only, read never.” Folks who’ve never worked with this stuff are the folks who don’t understand this point and brag of their supposed insider knowledge.
Getting out of the service or leaving a clearance-required job is not blanket permission to blab all you learned in the job. Rather the opposite. It comes with a lifelong obligation to shut up about the stuff, and the stuff about the stuff, and the clearance associated with the stuff.