numbers don't match

[Matthew W Peterson <pete-3@juno.com>]

Hello,

I just discovered a new characteristic of my car, the engine numbers
don't match.  The number R-61661 is stamped on the info plate but the
engine is stamped R  15877.  Didn't the post 67 R engines start at the
number R-40000?  If so what is my engine from?  Is it from an earlier
roadster, or something else?  I am totally stumped.

Thanks,

Matt Peterson
'68 1600  (almost ready to hit the road again!)