They aren't a bad old saw in spite of the bad rap a lot of folks have given them.It could have been made in the late 70's,they all had chain brakes.
The chain size is 3/8 " .050 .They came new with either a 16" or 20" bar ,so most likely that 24" was an after thought. Around 1980 ,K-Mart sold them for $169.95,with a 16 " bar.They were around $250 when they first hit the market.
McCulloch sold a bunch of them.
My 610 has worn out 4 bars and is on the 5 th.Most likely went through a 5 gallon bucket full of chain loops.I've always ran it on 32 to 1,old school,ya know.It doesn't get used that much any more but the old gal will still do a good days work in spite of being around 30 years old.
My one suggestion on that saw is to periodically check the fasteners because it will shake them loose.The anti vib really is not that bad though .
Most of the hard starting problems are stiff innards in the carb.On mine believe it not,I've never had the carb off in all these years.
Oh,I nearly forgot,keep the saw dust blown out of that saw on a regular bassis.The danged solid state ignitions will give you fits if they over heat,which they do if they don't get air.You can tug on that thing til the cows come home and no putt putt what so ever until they cool off.