Parforce horn is a hunting horn in the German tradition. A brass instrument, a simplified French Horn.
Google will translate German information on the Internet into English.
"Parforce horns are primarily used in hunting for blowing hunting signals . The large curl allows you to put your head and arm through and carry the horn over your shoulder. This leaves both hands free for riding."
Fürst Pless Horn is a smaller type of hunting horn.
Again, Google Translate is your friend.
Furst Press Horn
"The Fürst-Pless-Horn is still used as a signaling instrument for blowing certain hunting horn signals, the so-called hunting control signals, in company hunts. In addition, the instrument is also used in hunting customs and in concert in so-called brass corps, e.g. B. at Hubertus fairs , also with Parforce horns in B , are used."