Two graders with the same serial number???

If you are that concerned most of the time the s.n. is stamped under the tag . Im not sure if the graders only have one tag ?

Hi, Folks.
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That might help to make up for the one that I was shown DowNunda on which we COULD NOT find a serial # - or any sign of a place where one might have been. Zero. Zip. Zilch. NADA.

Are these characters stamped onna tag or into the frame?

If onna tag, have your friendly local welding X-ray inspection outfit come out and X-ray through the tag to see if it can pick up any stamped characters under it. Or just rip the tag off and have a look. Your description sounds to me more like a 9K series.

Just my 0.02.

On the 9k and the 8T have two tags one is on the right side of the engine just below the mag on the pony motor. The other is on the frame nose up by scarifier mount on the left side. The early 8T1-8T14781 (1954 100Hp) has few identifiers from the later 8T 8T14782 (1954 115Hp) . The one main identifier between the 1954 but not always is the starter boss for Direct Electric Start is pre-cut starting in 1955 (8T15523 - 8T17500). Some have said there is SOMETIMES a third Serial Number location. On the block flange where oilpan bolts on up under the injection pump on the right side of the Diesel. The oilpan flange is about 3/8" thick somewhere on the edge of the flange may be the elusive third stamped Serial Number. Good luck, I'm still looking for mine.
Other than that the Casting Codex number on different parts can help narrow down the year and serial number. Casting Codex numbers are 2 - 6 letters between two screw heads that have been cast into different parts. Not all Cat parts have a Casting Codex on them nor the same part from machine to machine. The oil pan on one 8T may have the Codex and the next one will not. The Codex gives one the day/month/year the part was cast. Castings were then warehoused "about" 6 months to cure, the larger castings like an engine block more so than the smaller items.
Another idea is a deep dive into part numbers the pony motor air filter was the definitive answer to lock down the S/N of my 1954 8T. Finding a part where the part number changes frequently is a big help. The governor housing is one such part. It takes time and is quite a rabbit hole. Good luck

Interesting about the casting codex. That would tell me if it's earlier or later, but it seems like the throttle being just the throttle vs. having all the gauges in it as well should also be an identifier. ??

It does appear to be a D318 motor, and is identical to ours in appearance, which rules out 9K I think...  ??

I am guessing that at some point, these two graders were under the same owner, and there must have been some reason to give them the same serial number... I don't really have access to the second one at present, but if get to it, I'll have to check the S/N on the motor. I would bet that it's tag has also been changed, since that one was pretty easy for me to find as well.  It would certainly be interesting to see what the block skirt has to say.  Someone did this on purpose, but I have no idea what that purpose would have been...

To be clear, this grader does not have an articulating frame as the owner claimed, and I would bet it only has a 12' moldboard, since there are no extensions bolted on... The only difference I see between it and ours is the throttle control being on a pipe and having the gauges in the throttle assembly vs. ours with the small throttle only control and gauges in the console to the right of the seat... 

Just blew me away when he sent some pics and one was the S/N, and it matched ours!!!

One reason for giving a "new serial number" would be to make a machine appear newer than it is to get a better price.

bank repossessed ? , bank got the wornout one , owner kept the good one

Fat Dan, Your Casting Codex explanation was interesting; I didn't know about the Casting Codex information. 

That casting code seems like an over-inspired, under-thought idea. Cat could have just put the actual date on, then there wouldn't be any need for this malarkey, or just not even had a date