How can you tell the difference between softshell and hardshell lobsters by looking?

Answer 1

Maybe by picking them up -- they will be light for their size. I don't think you can tell too much by looking. Also, I guess you can tell by the time of year:

"Every June, hardshell lobsters shed their shells to grow. A soft new shell grows underneath the old hard shell. The back of the old hard shell splits down the middle and the lobster pulls its tail, claws and legs out of the old shell and becomes a softshell or new shell. Over the season, the new shell will harden and become the next season's hardshell lobsters. Soft shell lobster season is from June through October.
~ Hardshell lobsters have more meat per pound than softshell lobsters.
~ Softshell lobsters have less meat per pound but have a sweeter flavor than hardshells."

Answer 2

When looking, the shell of a soft shell lobster is very translucent in comparison to a hard shell lobster. As the lobster is molting, the shell becomes very thin, therefore very translucent.

Answer 3

The best method I've found is to squeeze the rear end of the body. If it gives very easily, it's probably a soft shell. If it seems fairly stiff and resists the squeeze, it is most likely a hard shell. I don't think looking will reveal anything and squeezing any other part does not give an accurate idea of how hard it is.