US Smoke rifle grenades

[hchris]

As I read there are two different types, the M19 Smoke WP and the M20 Smoke HC.


The question is, what is the difference between the two models?

The more important questions, when were they available in the field? Around 1940?

http://www.lexpev.nl/grenades/americ...19smokewp.html

http://www.lexpev.nl/grenades/americ...20smokehc.html