@lorp It is a traditional variant form that is probably familiar to most Cyrillic readers. Just think of it as Т with really long serifs on the end of the bar.

The same construction sometimes occurs in lowercase even when the uppercase is the more famliar Т shape, as in Gabriola (below), and is what leads in cursive to the lowercase italic т looking like a Latin m.

@lorp Fontfabric’s introductory article on the origins and development of Cyrillic script shows some examples of this form in use in poluustav (semi-uncial) and early cusive styles.

https://www.fontfabric.com/blog/cyrillic-tradition-origins-and-inception/