Silver Star Classics has compiled one of the very best buying guides for the SE coupe and cab. Finding chassis numbers and knowing what they mean is a common source of frustration for owners and those looking to buy a W111 or W112 car. Silver Star Classics also has an excellent pictorial explanation of where to look to find the elusive numbers. Please enjoy their research and we will add more info in the near future.
Buyer Information on SE Coupes and Cabs
Beware When Buying a Cabriolet; Spotting a Fake

MB Spares in Australia has a fine tutorial that helps explain what the numbers in your car's serial number mean and why they appear in the order they do. Great reading for the owner who likes to know everything about their car!
Understanding Chassis Numbers

Buyer's Guide