We will do some checking, a key question is what manuscripts like Vaticanus and Alexandrinus have for the Sigma.
Kirk is very strong on that stuff, and we just did some zeta study, where the Cyrillic zeta and ksi (Xi) are also a Slavonic Greek of perhaps the 7th century on. However, these specific letters were often in overwriting and not ascribed to the first hand, even though it included Isaiah section numbers which were not overwriting. Most of that should be in our pages here, fairly easy to search.
Feel free to come up with more.
We have deep appreciation.
Also chat on Facebook Messenger is possible, and the groups PureBible and Sinaiticus and Textus Receptus Academy all have their strengths.