If you have just arrived on the classic car collector scene, you may have noticed a ratings system of sorts, expressed as a number from one to six. The intent is to establish the condition of the car.
The system is both simple and effective, ranging from 1 (the best) to 6 (the worst).
1) This is a perfect car in every way - no matter how close or where you look, it cannot be faulted. To qualify for a number one status, the paint would have to be excellent, with the usual flaws - orange peel, overspray, surface irregularities - completely absent. Off fitting door panels, signs of fluid leaks, any wear or tear in the interior, scuff marks etc. can cause a car to be denied a #1 rating. All parts, even the smallest nuts and bolts, if not new, will be refurbished. Essentially the only cars that qualify for this rating are those that have recently completed a no expense spared ground up or rotisserie restoration.
2) This is a car that is in excellent condition but does have minor flaws. They should however, be the sort of deficiencies that only reveal themselves on close inspection. Minor defects, such as paint that has aged, slight chrome misalignment, and some road dirt here and there will put a car in this rating category. "Show Quality" or "Museum Quality" rated cars are typical of a #2 rating. Older restorations are usually rated #2.
3) Defects are of a higher order and easier to spot. Occasional body panel dents, typically no bigger than a fist or slight paint mismatches are the sign of a #3 car. The interior will show noticeable wear, especially where the driver sits. Some chrome pitting may exist. Cars with a #3 rating should be reliable in that the owner has a reasonable expectation that they can be driven a long distance without a breakdown. They are sometimes known as "Drivers", the implication being that the owner can feel free to drive the car as often as they like since road dirt or other wear and tear do not significantly devalue the car.
4) At this point, the defects are many and obvious at a distance. Parts - for example exterior and interior trim pieces - may be missing or incorrect. Non safety related items, such as the radio, may be non-functioning. Evidence of poor / amateurish repair jobs will be apparent. Engine compartments can be filled with grease and grime with various fluid leaks apparent. #4 cars, while they may have all the safety items working, would not be considered reliable transportation. Body rust may be apparent.
5) Beyond having defects that will be obvious to even the non-trained observer, a #5 car, if it runs at all, does so poorly. Safety items are usually compromised and so they should not be considered road worthy. Rust is often apparent. Cars with this rating are in need of either a full or sympathetic restoration.
6) These are essentially parts cars; their only value are the parts on them that can be used to help other cars with a better chance of leading a useful life. Rust, which is brutally expensive to fix properly, can be prevalent. As a general rule, #6 cars, unless they are highly valued, are not good restoration candidates.
Notes
Very few cars will get a #1 rating. To put it in perspective, even new cars in a dealers lot do not qualify since detail areas, such as water spots, paint preparation or other slight defects will disqualify it.
There's another interesting aspect to a car with the top rating. Driving them, even occasionally, will subject them to slight amounts of wear and tear. Although strict and constant detailing can diminish this, keeping a car in #1 condition AND driving it is unfortunately mutually exclusive. This raises a point: is a car that you are hesitant to drive still desirable?
Often times "+" or "-" is added to the rating as a way of expanding the range. A car that isn't quite a number 2 but should be considered better than a number 3 might be rated as a "3+" or "2-".
Perhaps this is obvious, but Point of View conflicts can come into play here. A seller might tend to rate their car higher, sometimes in an effort to get a better price or maybe as a natural tendency to discount flaws in a car they are close to. A discriminating (critical?) buyer on the other hand might claim a discounted rating as a way of protecting themselves or to gain a price advantage.
Collectibility Rating
This is on a scale of A through F, with A being the top rating. The intent is to grade the desirability of a given car to car collectors. Factors that determine the rating include styling, performance, technical innovation, competition history, rarity and the cars' overall impact in the automotive world.
"A" rated cars are like blue chip stocks which, although highly valued, still have an excellent expectation of appreciation. Examples include the high valued classics such as Duesenbergs, Bugatti, early Ferraris and pre-war Alfa Romeos. Corvettes that qualify for this exclusive realm include the five Gran Sports racers and well optioned mid years 'vettes.
"B" cars are typically less rare than their "A" brethren. While they don't offer the stratospheric prices and appreciation potential, they can be said to be great investments if correctly bought. While less rare, their interest amongst collectors is high.
Cars with a "C" rating, although they still have attraction to car enthusiasts, are comparatively common. Their investment potential is medium in that while they probably won't loose money, they are not likely to appreciate. The upside is that they typically are affordable.
A "D" rating: these are cars that, while there is interest in them amongst car collectors, that interest is not widespread. Typically they only "float the boats" of collectors who are interested in a particular niche.
The Points System
This is based on a percentage like points system, with 100 being the top rating. It's generally used in concours events and is a measure of how "correct" (in other words, how close to original or factory built) the car is. Basically all cars start out as 100 point cars and then the judges, as they find flaws or discrepancies, deduct points. Similar to a car said to be in #1 condition, 100 point cars are very rare.
"10 footer", "20 footer"
A loosely based moniker usually reserved for cars with serious needs. It refers to how far away you have to stand from a car before the defects become apparent. If you are 10 feet away and the problems are quickly noticed, the car is said to be a "10 footer". A car whose problems are apparent with a 20 foot distance is a "20 footer" and therefore in worse shape than a "10 footer".