HP serial numbers

[PeterG]

Thank you Bob and Steve. I do now see that Bob is correct and that each 15C has a unique serial number for a particular week. Unfortunately it is no guide to how many were produced in a week.

I have read through Professor Kahan fascinating although somewhat periphrastic interview, linked by Steve, and here is a further extract relevant to 15C production:

KAHAN: “Well, when we then had these things going, it was time to build the HP 15C, and I had to persuade them to do it. Here, again, is an unfortunate story. …… I came to some conclusions about how many should be produced, and that was part of my argument for producing this calculator. The people with whom I worked most directly also wanted to produce this calculator. The marketing people, however, had done their own survey; they came out with some number which was half of mine, and I have no idea how they got it. It could be that they just took my number and said, “Oh, he’s an enthusiast. Let’s just simply half it.” Maybe they did that, or maybe they did their own research. I don’t know what they did. This was to have a devastating impact later because, after we got the calculator microcoded and everything was done and we had it tested and running, the marketing people then told one of our guys how many they wanted produced. It was this half of the number I wanted.
Now, fortunately, the guy they told it to was Dennis Harms, and what Harms did was to build a roboticized production line in a room that was about the floor plan of this house, maybe a bit smaller. He had a roboticized assembly line which, on the end, cost Hewlett-Packard 20 seconds of human time per calculator, from unloading the stuff they purchased from vendors at the loading dock to loading the cartons full of crated computers to be shipped out to their sales outlets. Twenty seconds of human time per calculator. This included jigs that tested partially assembled components. Now, if my memory serves me rightly, this is one of the tricks they used: a partially assembled subcomponent went into the jig; it got tested. If the test failed, this component got moved by the robot and put into a bin of rejects. Otherwise, it went to the next stage on the assembly line. And these things went faster than fingers. I tell you, I saw it working. They really went fast.
What happened to the bin of rejects? Well, somebody went through the bin of rejects and looked to see whether the rejected parts had a little red dot of paint on them and, if so, they went to the crusher. Otherwise, they get a little red dot of paint, and they go back into the supply bins. Of course, it was this partial assembly that went into the bin, but it was then disassembled; the individual components on the assembly got these dots, and they went into the stacks that were going to be used. So, you see, instead of having to diagnose an assembly to see which of its parts was defective, what they did was try it again later, and if it got rejected twice, then forget about it. All right, so some good parts would get rejected, and on very, very rare occasions, perhaps, something defective might get through. But they had very few returns. Texas Instruments used to have a return rate that ranged from a third to a half of their calculators being returned as defective. I don’t think Hewlett-Packard’s return rate for all causes, including the fact that somebody regretted the purchase, ever got as high as ten percent. So these calculators were being produced and, my guess is, it cost them something under $15 to produce, maybe, as little as 12 and you send it off short, but it gets sold in CompUSA for 70 bucks. So there’s a lot of room for mark-up along the way.”

Quite astonishing that it took about 20 seconds of human time to produce a 15C calculator.