Tom, I can't say for sure, and I doubt anybody could really, but all the indications I've ever seen or heard of had the 55's using the stork. 55 being the first year for the 3 piece case, they routed the temp bulb into the block between the fan housing and the firewall. Earlier two piece case cars had the dipstick type. But that's not saying a VDO couldn't have been factory because as you know, Pre A's are prone to what I call "Pre A Weirdness". My 55 coupe (53739) had the stork. But the line was cut so I bought the Palo Alto replacement clone and it is really nice.
Another oddity is that the Beck "pump" system fuel gauge ended with 55 coupe number 53527 and later 55 cars had the VDO electric gauge. This VDO gauge was only used for the remainder of the 55 model year. Your car, being before the cut off has the beck system,...mine has the VDO. Neither are easy to find these days.
BTW, I also have a VDO oil temp gauge, which I used in my engine test stand. It is date stamped on the back 7/56 so maybe you could get a look at the back of yours and see if it's stamped. That would clear things up eh?