Th
Old images from online.
MAC (always cheap metal that rusted on seams and welds, spot welds for baffles visible on shell, no markings and very square or rectangular with sloppy welds around flanges):
View attachment 1739890
View attachment 1739893
---
Flowmasters (40/44, silver or black) are very distinct with seam on shell, stamped name, oval can, clean flanges, and in many instances the circular "bump" on end of can:
Those MAC are it !