I though I would pick up a couple of these at $4 each as spares. One slight problem, they are missing a post. All 914 flashers early and late have 4 posts. Aren't reproductions supposed to be correct? It would cost almost as much to return them as they are worth.

Real ones are $50 each. Rich at high Performance House has real ones.

If you ain't returning it, plug it in to see what it does. Is the cover a ground or "the 4th" post?

It is possible that the missing post is the K/C2 terminal which drives the dash indicators. You can work around the missing terminal.

I bought 2 of them and threw them in the drawer - didn't even open them.

I took it apart to see. BTW the coil is 24VDC:
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Click to view attachment
Click to view attachment

I also found this schematic online:
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The range anywhere from a $14 and up depending on where you shop. What they are selling are for VW not 914.

I saw some 4 lug versions for $14 as well. Several sources.

A real flasher relay has 2 coils and 2 sets of contacts inside. One set flashes the exterior lights and the other flashes the dash indicator. That is why they have 4 terminals.

Is it just a DPDT?

No. double coils, double single pole.