Very pretty! I’m not seeing great similarity. For one I can’t tell if your beads are stabilized or natural, as in the Four Winds Bisbee necklace. Yours seem notably greener stones than the Four Winds turquoise. Also, the heishi is different, yours being dark penshell and FW being lighter tones. A lot of dark penshell heishi was Asian import material.
Without an expert in-person valuation it’s hard to say. (You’d also have to know that your late MIL was likely to have owned expensive turquoise beads.)
Thanks @chicfarmer! I know the likelihood wasn’t good that they are Bisbee.
It’s the brown matrix that puzzles me, so I had to ask if anyone had an opinion.
She had a wide variety of jewelry, including a bunch of NA, but nothing great that knocked my socks off.
Like most people, she didn’t have a clue about quality in jewelry, she just liked what was pretty.