15thc perception on swallowtail merlons?

[Pierre Dumont Himself]

 I've seen the Castello di Brescia is included in the Map of swallowtail merlons. But I think the swallowtail merlons in the picture are not the medieval ones: according to wikipedia

I'm going to need more time with Brescia because of its complicated urabn history, but you are right about the castle. The merlons were added for the 1904 expo, when the castle grounds were opened to the public for the first time. In the late 19th century, the castle was used as a prison, and Captain Sorelli oversaw its renovation using prison labor in preparation for that expo. The merlons are clearly visible in photographs from 1904, but not in 1897, 1898 or September 1900. 

Photograph from 1880, before Sorelli's interventions. 
Unfortunately, I couldn't find any trace of the merlons in contemporary images, but I assume they wouldn't have been mentioned if they did not exist. There is also independent evidence that the castle and the walls had swallowtail merlons in the Middle Ages, which I will hopefully be able to present this week.

Torre della Bruciata:

Nowadays the clefts in the merlons have been filled (I don't know when).

It doesn't really matter if it happened in the late sixteenth century, when the gate was rebuilt, or at some later date. The merlons (and the gate) were also repaired with brick, but the crucial point is that at least some of them are made entirely of stone, which was the only material used in Brescia until the early 15th century.

 Torre della Pallata
One of the city landmarks. The merlons are however late, they were added between 1476 and 1481.

You have to thank the Venetians, whose archives survived better than anyone else's. 

 I know of two other buildings in Brescia with swallowtails merlons.

There is also the Torre del Pégol in the main square, whose swallowtail merlons were added in the early 19th century by the architect Rodolfo Vantini.