Unknown .577/.450 Martini Henry cartridge

Help please! I have this two-piece case construction Martini Henry cartridge in my collection. There’s no headstamp. Who made it and when was it made? Does it have a specific title? Thank you in advance for any help.IMG_1836

That is a one piece case, known as a “step-base” case & the thought it Kynoch was the maker.
The step-base case is also known in the .577 Snider, and is thought to be an early gimmick to transition from the coiled / rolled case to the drawn brass case.

Thank you Pete. What do you think the date (more or less) of manufacture was? F

I don’t know as there was a longish overlap of manufacture of both drawn and coiled cases, that said the first published Kynoch catalog (1882) does illustrate this case as .577 reduced to .450