Please help identify Stax Lambda Pro.

Hi all you Stax earspeaker users.

How can I tell wether a pair of Lambda Pro's are actually Pro's and not simply regular Lambda's?

Thanks in advance.
You may want to do a search both here and audioassylum. I thought the Pro's were slightly different color. dark beige or light brown as opposed to the std. black offerings if I remember correctly. I have the newer SR 212 which are concidered part of the older Lambda series. Maybe someone else can chime in who has more info..--best of luck--Ken
You can tell by the connector. 5 pin connector (pro) v 6 pin connector (regular) - think I've got that the correct way round. Regards, Richard.
I have a pair of Lambna Pros.. they have 5 pins, black in color. I don't know what the "regular" ones look like..
I am using mine with a new Stax tube amp, the 07t or something like that.. I feed it from my benz phono unit direct. way better than the 'black box' the lambna's come with. I'd like to know how much better the real expensive new Stax units are over these Lambna pros.. mine are about 14 years old now.
Thanks guys. Any thoughts on the new 4040 cans compared to the pro's? What about long term reliability of the Pro's?

The 404s are an improvement on the same theme. A little quicker, a little more bass and h.f. extension. Definately from the same family. The differences are not dramatic, but they are there, nonetheless.