How can you tell lif you have a cone of serger thread or piecing thread
 

I was given 5 cones of thread. They are 80 wt. I know that sometimes people will use a lighter wt for bobbin thread, but I'm not sure if there is a difference between serger thread and regular light weight piecing thread. It seems to be very nice quality, no little hairs like some heavier threads I have.
Not sure how to tell the difference.
Thank you for any input!

Is there a brand name on the cones?

Yes Nammie...it's MIRA thread, 60% PES 40% cotton (I'm not sure what PES stands for)
I guess that brings up another question.......

PES is a polyester material.
The great thing about having an older machine (before computerization) is that all kinds of thread can be used. If you have an older machine, you can try this thread. If it doesn't work, maybe you can find another use for it. I use all kinds of thread on my older sewing machine .... for different effects. I've also put a lot of thread out for the birds and such that didn't work for me.

For piecing I've been successful with all kinds of thread.

For FMQ quilting, not so much. My machine (Janome 7700) seems to love 40 wt. embroidery thread for quilting! It never breaks! :) Straight line quilting for me is much like piecing--can use what I have. I've been the fortunate recipient of different people's thread, so I try to use it all! If I can't use it in the top, then I wind it on to bobbins and use it while making scrappy tops.

do a 'tug test' to see if it is strong thread- if it does not 'readily' break when a piece is held between your 2 hands and given a tug it is usually strong enough for piecing. I know some people don't want to use thread that says 'serger thread' on it - but I have successfully used literally hundreds of cones of serger thread- my mother bought a whole *going out of business* inventory of serger thread one time & we spent years using up all those cones ~ the thread worked fine for piecing and was even good on the long-arm with the high speeds that many threads do not handle. we did have a few cones that were 'weak' did not handle a strength test- we did not use those for piecing/quilting. those were set aside for serging or embroidery that uses many threads to make up the design.

I have used serger thread as I had 4 and was not going to throw away as it cost a lot. It pieces beautifully.

I tried serger thread on my LA and it did not work.

You might try doing a search for MIRA thread and see what you can find there. That is usually how I find information on different threads that I've purchased and can't remember what they were purchased for.

I have been using serger thread for piecing for so many years now and never had a problem.