Engine ID

[imscience@juno.com (G L Cook)]

My B has a one year old commercialy rebuilt motor, rebuilt in the U.K.. 
The aluminum motor ID tag is gone and in the cast iron area beneath where
it should be is punched "DEK 0077C 32-4"
I was told the motor was a "chrome bumper" MGB type.  Because specs vary
widely for the various 18V... motors, how can I tell which it is?  Right
now I tune it by ear (pinking only on acceleration on hot dry day with
<92 octane), but the question of replacement parts is inevitable.  Any
other distinguishing marks?