Mike Sebastian has a substantial amount of information regarding the integrated circuits used inside vintage calculators. You can see his website here.

I have a CT5002 chip still in the package. Here's the pinout data from Mike's site, but I'd be interested in seeing full schematics for a calculator using this chip.

Cal-Tex Semiconductor, Inc.  CT5002 - 12-digit calculator, 4 function
              _____ _____
             |     U     |
 (Gnd) Vss --| 1      40 |-- Ø1 (out)
  (out) Ø2 --| 2      39 |-- Vdd (-6V)
  Clock in --| 3      38 |-- Display Inhibit
  Neg Sign --| 4      37 |-- g
        N1 --| 5      36 |-- f               N1, N2, N4, N8 are number inputs
        N2 --| 6      35 |-- e                  using diode matrix keyboard 
        N4 --| 7      34 |-- d                  encoding
        N8 --| 8      33 |-- c
      [CE] --| 9      32 |-- b
       [C] --| 10     31 |-- a
       [-] --| 11     30 |-- dp/overflow
       [x] --| 12     29 |-- P2              P1, P2 are decimal point placement
       [÷] --| 13     28 |-- P1                 inputs for 0, 2, 3, or 4 places
      [+=] --| 14     27 |-- D12
       [.] --| 15     26 |-- D11
        D1 --| 16     25 |-- D10
        D2 --| 17     24 |-- D9
        D3 --| 18     23 |-- D8
        D4 --| 19     22 |-- D7
        D5 --| 20     21 |-- D6
             |___________|