The most important aspect of the Sterling is whether the car is in running condition. I have never seen a Sterling that was complete sell for more then $3000 if it was not running.
A very close second in determining a Sterling's worth is what type of engine the vehicle has. The typical engine in a Sterling is a 1600 CC VW Bug engine. The problem with the VW engine is that it sounds like a VW engine. Who wants a super-exotic looking car with a pingy VW engine? Any upgraded size engine from the 1600 cc increases the value of the Sterling and usually increases the performance. In the USA, American engines are the most sought after and Sterlings with them sell for more money then Sterlings with VW engines.
Something else to consider is how 'complete' is the vehicle? If the Sterling was built by someone other then the factory, it may be missing small things. It was not until the day I sold my first Sterling that I realized it did not have four-way flashers. A few other things to check for are: radio, adjustable seat, horn, interior light, and defroster. Defroster is VERY important if you live in places where it gets cold in the autumn and spring. Since you sit so close to the windshield, your breath easily fogs it up.
There are other vehicles that look similar to a Sterling but are a little differert in one way or another. The Sebring was almost identical to the Sterling except it had a higher roofline which allows for taller people to own it. It also did not have the rear louvers. I think all Sebrings had pop up head lights. These sell for the same price as the Sterling. The Nova is basically a Sterling produced in England. The Cimbrea on the other hand is extremely rare. It has the body of a Sterling with gull wing doors like a Delorean. I have never seen one in person. In August 2000 there was one for sale in the Ohio area for $8000. This seemed expensive since it only had a 1600 CC engine.
I have used many websights and references as possible when compiling my price guide. With the exception of e-bay, I do not know what the car actually sold for, only the owners asking price. Mileage really make no differance on a car like this since most of the time, the Odometer does not read the true milage anyway. What does increas the value is having a paper history of the car. This includes the original build manual, the reciepts from all the work done, and the documentation required by the DMV.
Fiberglass Body only $1200-$1800
Complete & Not running $2500-$3000
Complete & Running w/1600 cc $3000-$5000
Complete & Running w/1835 cc $5200-$5500
Complete & Running w/2100 cc $5500-$6000
Complete & Running w/ V6 $5500-$6500
Complete & Running w/ V8 $6500 +