Let's be guided by the facts: here in the photo you can see that the tails are the same, with five holes:
And here the howitzers aiming flywheels have the same diameter:
Perhaps a scaled barrel was produced, for a smaller caliber - 149 mm. Are you sure this photo is not Photoshop? It looks suspicious. Most likely - photoshop.
In prototypes of 210 mm howitzers, the breechblock opened to the side.shultz wrote: ↑21 Mar 2021, 17:02P.S. , the original caption of the photo of the barrel on the "FondazioneAnsaldo" site says "149/40 gun" but it is a mistake, compare the breechblock with that of the 149/40 .... of the series specimens where the breechblock opens towards right (in the prototypes it opened upwards).