> >The "9915" code refers to "Year 99", "Week 15" that is, near the end of
> >April.
> >I don't know about the "B3P" suffix.
>
> Rev level of silicon in Plastic case.
> I have a B2 rev, so you're one up on me.

Not quite.  The "P" for plastic is at the end of the part number, not the
date code.  For instance, the part I received at the seminar is marked:

        PIC16F877-ES/P
        9908BSP

The "ES" is for Engineering Sample.  For production parts, ES would be
replaced by the speed grade, or "JW" for a windowed part [*], or "ME" for
a bondout.

After the date code, the first character designates the facility in which the
wafer was produced, the second character is the mask revision, and the
third character designates the facility in which the part was packaged.

So a "B3P" part has mask revision 3 (not "B3").

The tricky part is when they use both letters and numbers for the mask
revision.  I'm not sure whether rev S is newer or older than rev 3.
One might presume it to be older judging by the date code, but there's not
always a correlation.

The markings are explained in the back of almost any Microchip data sheet.
For instance, in the 16F877 data sheet, document DS30292A, it is in
section 17 on page 179.

Eric


[*] Obviously they are not likely to put flash parts in a windowed package.