Excuse me Tom, but I'm not sure I can understand you clear enough
You're asking me about buttcap, but which sabre do you mean? sorry. About the Batory's sabre I can't give you it's measurments by now, I know this sabre only from this picture, but I'll try to look for it in catalogs.
"Interlocking knucklebow" - do you mean knucklebow attached to the pommel ? I think it has appeared in 18th century. Excuse me once again for misconception.
Ariel: Janowka sabres are rather rare, and this post treats about most popular and famous dedicated sabres: Batorowka and Zygmuntowka. There were also very popular Augustowka sabres in use through whole 18th century, but there you can see only a cypher of August II and August III on blades, so I think they're less interesting.
About evolutionary you're asking. Again I'm not sure I can understand you clear, but if you're asking about sabres itself I think we can not call it evolutionary in any way. Batorowka and other dedicated sabres are
not separate type of sabres but just a sabres with imagination, cypher or bust refered to king. If you'll find a modern sabre, i.e. from 20th century with a bust of king Batory on a blade, you can call it Batorowka as well. If you're asking about evolution of Polish sabre (what I belive you know very well) I can invite you to my previous thread about polish hussar sabre, where I belive you'll find something intereting
(
http://www.vikingsword.com/vb/showthread.php?t=67) . But if you're asking about evolutionary of the imaginations depicted on blades... there you can see evolution, no doubt.
RATHER: Just let me know when you'll be next time in Krakow, I will show you them with great pleasure. Unfortunately our gallery of Polish arms and armour is temporarily closed, but there is no problem for me to open it just for you
My email is at your's disposal.