If memory serves the saw is a McCullah Pro Mac 510.  It started out as a 10" bar and now has a 14" one on it.  During the years as a bar wore out I upgraded to the next size, the 14" is the biggest I can get.  Four years ago I put my latest bar on the saw.   The drive sproket has been welded and trued, I'm a machinist, and I've made a new exhaust cover for it out of alluminum scrap after the original was lost.  The last few years I've added what I consider an appropriate amount of carb cleaner to the fuel mix twice during the summer.  The saw is still basically yellow but the name is scratched off.

 

I bought the saw in '78 to section our old house that we tore apart to build our new new house.  Those two days I quartered and carted walls to the dump cost two chains, but the vast majority of the saw dust and chips used for insulation in the walls managed to get to the dump (as landfill sites were so appropriately named back then)

 

bigguy