An Unusual Portrait Of Vespasian

Not the usual portrait indeed. Very nice pick and it seems you have a very keen eye for Flavian oddities - Good Job -

On of the most common of reverse designs for aureii and denarii for Vespasian.

I agree that the portrait is unusual.
I did a quick visual comparison of other portrait styles for Vespasian on Vcoins over some hundreds of coins, looking for similarity. This style appears unique despite the fact that there is great variation in the portrait styles of Vespasian from many mints that were spread far and wide around the Roman Empire at this time.
The die cutters' styles would have been affected by their own local culture to some extent.

I also notice that the pictured coin was struck early in the reign of Vespasian. For a die cutter to have some idea of what the new Emperor looked like, a plaster bust of the new Emperor had to be sent to each of the mints around the Empire. Until a new plaster bust arrived at the mint the die cutter would have little or no idea of what the new Emperor would have looked like. That may have been the case with the effigy on this coin.

To get a better idea of how Vespasian appeared in real life go to:
Google Images: 'Vespasian bust', and look at a range of images that can be found there.

As an aside, (I don't think this the case here), one of the ways a fake coin can be identified, is by style.
Style variation is one of the more obvious ways that fake U.S. Territorial fractional gold coins are identified.

just an assumption :
if you compare the coin RIC2,1,921 , a coin of Domitianus of 76 CE as Caesar , I think there is some similarity .
In 70 CE , Domitianus was a Young man of 19 years old , so maybe he was in Rome and the celator took him as model . albert