Picked this up at a gun show today. Looking for opinions on what I have. Is the body a Mk2? I see yellow paint under the blue. 

Post war US M21 practice 

What about the yellow paint? Would that indicate a Mk2 body modified for training use? It looks old and under the blue paint. Any reason to paint an M21 body yellow? 

Shouldn't ever had yellow paint on it originally. Since it has a perfect center hole and its a type 4 body, it wouldn't have been a HE body converted to practice. Most yellow mk2s were type 2/3 bodies, there were some type 4 bodies that were yellow but that was earlier in the war before the color change. And even at that time the practice bodies were different, with an offset threaded hole, usually they used reject bodies for practice MK2s and early M21s. Later M21s have perfect center holes and then chamfered holes as well. 

 

Paint on Mk2s is hard to tell originality sometimes, because so many have been repainted and missed with over the years, especially when there is layers of paint. But as it sits in current form, it is what I said, an M21 practice. 

Not to be contrary, but can you explain type 4 body versus 3 versus 2? 
 

Also, the segments on this grenade are more squared off than the M21 grenades I see on the net.
 

Finally, I don’t believe the bottom hole on my grenade is chamfered. shouldn’t an M21 have chamfer? 

https://tgrm.foxed.ca/Americangrenades/Mk II/The Mk 2 grenade.html

Good resource. This is listed as a Mk2, shape and segments looks very similar.

 

 

Yours is not a MK2, it is M21 practice. That yellow MK2 HE has a solid bottom. 

 

Also that is not a MK2A1, an MK2A1 was released after the color yellow was used. You confused the title under it with it. The title comes first then the photos. It is listed under the MK2 section. 

More yellow MK2 grenades had filler bottoms than solid bottoms.Solid bottoms were late,filler bottoms were early.Early WWII greandes were yellow.

The MkII grenade body with the M10A3 fuze was designated MkIIA1 to distinguish it from MkII bodies equipped with previous fuzes such as M10, M10A1, and M10A2. Some of these grenade bodies contained a tapped hole and a metal plug in the base, while others had a solid metal base. The decision as to whether the plug was used or not was optional with the manufacturer.

 

It is to be noted that the MkIIA1 grenade differs only slightly from the defensive hand grenade, MkII used in World War I. During the years 1918-1940, the filler was changed from Trojan powder to EC blank fire powder for reasons already stated. The most significant change occurred in the fuze. The early model of this grenade was equipped with a detonating fuze. The 1940 model, however, was provided with an igniting type of fuze, M10. 

Due to the fact that we ordered the color code change in Dec 1942 and the sheer amount of grenades in production and in the field at the time, it's completely possible to see a flat bottom grenade with Yellow under Green paint.