What you have is a ECO Salesman Sample. It should have the base on it as in the picture.
The other thing that ECO had on the top of the housing frame was a little handle like card holder.
When the ECO 90 Series first came out they though it would be a good idea to have this little card holder with a card in it stating when the last time the unit was calibrated. A new card was put in each time the rapair man calibrated the unit. I don't think this lasted too long. What if the date was 6 months old, would you trust the meter? And how could you expect the owner or a repairman to be calulating the unit ever week or so? I don't believe the service station owner cared much about the ECO out there, after all, he just had to buy something in order to give something away. Now he had to repair it because the driving public abused it all the time.
This is an original Bennett factory photo.
I once had a unit with two holes in the frame, but I sold it before I found out what it was for. If I remember correctly it was for the one that held the card.
Author, Gas Pump Identification book, Air Meter Identification book.
[This message has been edited by Jack Sim (edited 11-27-2006).]