Trying to figure out the production numbers of these cars, I found several sources that were different. some books say 1163 for the 2.0 and 420 for the 2.4 but Mike Morris in his book details why 1133 and 424 is correct. I find it odd since Mike's book came out before Gabriel's book and in his book Gabriel uses the usual 1163 and 420.

The first 25 cars built were test cars or mules as they are known in the auto industry, they were not sold and were destroyed.

It should be noted that between 1970 and 1971 there are 7 cars missing in FIAT's records, this is from Mike Morris's book. Jean-Pierre Gabriel's book does not list the 7 missing cars goes directly from 001371 to 001372. Mike's claim in his book come directly from observing actual FIAT documents however the cars were built as Mike Morris says in his book that he knows of 2 of the cars in the missing gap.

The serial numbers are in 3 places, stamped on the manufacturers plate in the engine compartment, stamped into the body below the manufacturers plate and also in the middle of the body panel underneath the windshield, you have to remove the windshield to see this one. The Dino is designated as Type or Tipo 135. The serial number identifies the motor size A for the 2.0 and B for the 2.4 so a 2.0 Litre Spider would be 135 AS 00xxxx and a 2.4 would be 135 BS 00xxxx

But arn't all FIAT Dino's 1966 or 1967 ? that is all I ever see advertised:
Most Dino's brought into the US were brought in after 1968 were subject to a new law the The 1968 Importation Regulation (19 CFR 12.80). Dino's did not meet this rule and since the makers tag does not identify the year of manufacture, it was easier to say the car was a 1966 or 67 FIAT and get the car imported into the U.S.

Sources :
FIAT Dino, Ferrari by Another Name : Mike Morris
FIAT Dino: Les Ferrari de Turin : Jean-Pierre Gabriel