Shin Matsubara 信松原

(信) 松原請合
信 ・ shin ・ trust / faith – framed by a crescent-shaped kane mark, likely serving as a brand or signature.
松原 ・ Matsubara ・ family name of the smith or workshop.
請合 ・ ukeai ・ undertaking / guarantee – used in blade/tool inscriptions to mean “guaranteed by” or “made by.”