Without the ability to calculate MOI in a putter, what features should be looked at to roughly determine MOI of a putter?

Example is walking into a golf store and looking at the putters in the putting area. I know a traditional blade-style will have a lower MOI than say a Mallet style but if you have an easy, quick look to get an idea that would be great.

I am also looking at the Tour Track Pure Milled as another option, but again, choosing without the ability to be fit makes it a somewhat stab in the dark choice.