I'm guessing you got the code breakdown from Yesterday's Tractors, from a post by Dad's 88. Blane got that from me, so if it's wrong, I'll take credit for it.

Here we go, by the numbers, or letters...

A 02 - The A code was the style. From what I have figured out, this is where the paint comes in. On some of the later models, I have noticed a pattern in the A codes between the Oliver (green) and Cockshutt (red). In the case of your tractor, this would most likely be the adjustable front axle, manual steering, green paint. Since this is in the base price, it doesn't show up in the dealer price manual. I would have to see some more 550 build cards from units that are known to be green to see which codes they used to be sure on yours.

B 27 is the engine, most likely a gas, but it doesn't show up since it is in the base equipment. B 54 was for the diesel engine in a 550.

C19 was the transmission, also known as 519, which should be the suffix on your serial number. This is the 13/53 bevel gear set, and appears to be the most common.

E12 Most likely code for regular PTO. Once again, standard equipment, so no need to list it in the price book.

F61 Is Complete hydraulic unit, minus three point hitch. Yours still has three point, but we'll get to that in the P code.

G13 Is 13.6-26 4 ply R1 tires.

H48 Is the E705B pressed steel wheel center.

I 47 is the ES7002-A rim. (12-26)

K04 is 6.00-16 4 ply front tire.

L 08 is the ES729 rim. If this were an 88 and you had cast iron front wheels, there would be an M code. Since it is a one piece rim and center assembly, there is no M code.

P 49 is code for three point hitch. It doesn't show up because it is standard equipment. It does show up in the 1968 price book for some reason, that's how I got it.

Q22 Is most likely the regular clutch, standard equipment and not listed in the price book.

R15 regular axles, standard equipment again.

S18 most  likely regular fenders, standard equipment again.

Z08 Most likely a single 12 volt battery. The only codes that showed up in the price book are the ones to order without a battery(s). Batteries were included with Olivers at that time. 

Once again, you can see where some of the confusion comes from, with codes not being listed and so on. Some of it you have to take for granted until you can compare a few build cards and start to get a pattern out of the numbers. Working with the build cards is like putting a puzzle back together. Sometimes the pieces fit easy, and sometimes you get stumped. But it sure is fun!!