Can someone tell me if this part number, 1268300384, is correct for an R12 or R134 expansion valve?

My repair shop gave me an estimate for $55 for one of these parts, 4 new "O" rings, 3 lbs. of R12 @ $45 each, and $150 labor to get my AC working. Total $342 + tax. I'm probably going to get the work done, but now, besides the question of whether this is a good price, I wonder if the replacement part will be correct? I do like cold AC and I do travel south at times. Thanks in advance,

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Robert W. Roe
1984 300SD 170K mi