I assume you mean "ADB" when you say "apd"? It hardly matters because, no, you cannot hook an ADB keyboard to the IIc's 5 pin DIN serial ports.
My guess is the dingus you found is actually a 5-pin DIN to 8-pin mini-DIN serial adapter, not an ADB converter. The IIc's serial ports were unique while the IIc+ and IIgs used the same 8-pin DINs as Macs from the Mac Plus forward so I can certainly see a reason why such an adapter might exist.