Soapstone Seal Translation
My interpretation:

肇　松
吉　原

The guess of「肇」is based on this variant of「肁」.

西周金耳尊集成6007隸定　

Together, this makes a Japanese name 松原肇吉 (something like Matsubara Tadayoshi).
You should post this on https://japanese.stackexchange.com to doublecheck.