Die Sinkers Chisels are just that,,generally used in the die cutting trade.
A trade that is almost extinct today with most all dies (marking, embossing, stamping/shaping, roll, ect) being made by machine processes.
At one time it was a very large trade in our industrial based economy. Most engravers were die engravers first,,and firearms engravers second.
Even the engravers working in the gun factorys had the job of making the hundreds of different punch stamps and roll dies needed in manufacturing. Plus they had to recut them when they became dull.
Die Sinkers Chisels are heavy duty for removing larger amounts of material than common gravers,,though they can certainly be used for engraving delicate lines too if sharpened a bit differently and in the right hand(s).
Some gun engravers used to use them commonly along with punches for shaping heavy relief style engraving.
They were used by gun engravers when sculpting and shaping of the frame and fences was done. Heavy work done easier with a stouter chisel and hammer.
Impression and embossing dies need large amounts of material removed to leave the (sometimes reversed )image raised. Add to that, dies that also form metal into a rounded or cupped shape with decorative details within that shape,,you can see where material removal needs to be removed quickly if any progress with thoughts of making a profit are in the mix.
The heavy one piece handle & point makes for a very sturdy chisel that does not vibrate in your hand.
Alot of the Italian engravers make their firearms engraving gravers the same way of one piece. But of much slender shape and delicate point.
Most die sinkers chisels available are in HS steel at best today. So they don't cut alot of modern firearms steels any better than a standard graver of the same material dispite their size.