Particularly those in which an apostrophe-backspace-period served as an exclamation point, I'd guess.
Depending on the language and the keyboard the straight quotation mark in typewriters was used for different purposes. Some examples taken from Mackay, The typewriting dictionary, 49–50 (from top to bottom, diaeresis, ditto mark, exclamation, feet, inches, minutes and seconds).
However the exclamation mark and the diaeresis were often included in the keyboard. I guess is a matter of style to use straight of curly quotes today. Actually, in Hebrew straight quotations marks are more common.
Every script has its own peculiarities and to reuse letterforms from one script to create another one is usually a bad idea. In Hebrew letters are reversed-contrast compared to Latin letters, the weight is in the horizontal strokes. My advice is that you should define the design features of Souvenir (endings and joints of the strokes, proportions…). You have to find the way to capture the essence of that typeface and translate it into a different form.
Nina, this is an image of the Libro Cassinelli an internal document used in Olivetti as a reference for typewriter type design (1969). The original document is in the Archivio Storico Olivetti (Ivrea, Italy). For further information and other references in type design for typewriters, look at the dissertation available in academia.edu. I would be glad to see more research in this particular topic.
It is true that the spread of the ink caused distortions in the shapes of typewritten letters, but it is also true that it was difficult that the ink reached the corners of the outlines so some type designs for typewriters included distortions in the metal face for getting a better result. Maybe I am wrong saying that American Typewriter was inspired by the design and not the printed letters, it was my guess. This is an image taken from a manual for the design of typewriter typefaces.
The good thing about creating classes is that you can use it in different lookups, without having to write the groups down more than once. If you are just going to use that group just once then you don't need a class.