What is this?

<p>I ran across what looks like a IIIc with a plug in the front. What is this for? A flash? I can't find anything on this. Custom add-on?<br>

Thanks</p>

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<p>Looks like a third party flash sync modification. There seems to be an endless variety of these, some uglier than others. I have a IIIa with quite a neat mod, a simple circular socket on the front. A factory mod would have put a socket on the back of the top plate and added a flash sync dial, just like the IIIf.</p>

<p>A technician can add flash synchronisation to a screw mount Leica prior to the IIIf (or to a copy). As Richard says, there is great variety. Sockets are of different kinds and their placement is variable.</p>

<p>Thank you for the responses, gentlemen. </p>