Scottish Sign Language does existed in 1800s.

Have you aware that there is Scottish sign language back in 1800s. It does existed. Ada should know the old language of Scottish. They need to research more on that before they go on movie. Actually back in old days called Deaf and Dumb alphabets in Scottish.

’Deaf and Dumb Alphabet. For the use of Deaf Mutes, and for the amusement and convenience of those who wish to Speak with the Hand and Hear with the Eye. “Manusvicaria Linguæ,” the hand performs the part of the tongue.’

Sign Language Guide published in the late 1800s or early 1900s

I am Scottish and Irish ancestor.