That's the bike I saw for sale on advrider. It has all the esoteric details correct for a very low serial number sandcast (black kill switch w/o pointer, long choke lever, smooth oil lines etc). Even the #8 bolts are slightly different from later sandcasts.
Sandcasts desirability is scaled by the number of 0's (zeros) in their serial numbers after the initial 1; CB750-1000001 thru 1000009 have the most possible desirability (5 zeros). CB750-1000010 thru 1000099 is the next most desirable group (4 zeros); CB750-1000100 thru 1000999 is 3rd group (3 zeros); CB750-1001000 thru 1003950 is the next interesting group because that's the last group w/ a left side horn (an ez way to spot an early sandcast). The last group is CB750-1003951 thru 1007413. Then there's the elusive CB750-1007414, which would make it the LAST sandcast ever made, making it ultra-desirable.
Of course keep in mind engine and frame numbers that match are EXTREMELY rare (I've only seen 1 example EVER) but the numbers are generally within 10% of each other.
Interesting point about the very early sandcasts: they came from factory w/ a bunch of parts that the dealers sometimes removed at 1st service as recalls. Which parts were not replaced? Does it have a smooth oil filter housing or skinny throttle cables? Curiously, later sandcasts share more parts w/ K0's (non-sandcasts) than they share w/ very early sandcasts like this puppy.
In my opinion its the best early unrestored original I've ever seen or heard of, and its condition in same category. I've seen earlier serial numbers, I've seen perfect restorations, I've seen unrestored originals. This example has all the right stuff.
And you should ride it, they have a wonderful exhaust note. The sandcasts are faster and much louder than K0's and later CB750's.
