Don't know the dates either started or stopped, but I can tell you with fact that they were both still in Vietnam in 69 thru 71. I had at least 3 M-15's, they were in OK condition but the fuze spoons broke off so those greandes were turned in. As for the M 34 carried a them, but normally only 1 maybe 2 at a time (they were too heavy). Threw the 34 twice, not something I would recommend unless you have an arm like P Manning. On the last one I threw had WP raining down around us. But they did make an impression on the NVA. The M 15 was still listed in the TM 43 sersis on grenades in 1977. The rifle grenade was the M-19 rifle grebde, left service in the early 60's. The M 34 was also used in the M 176 smoke launcher that was mounted on the turrets of Sheridan Tanks, it launched a M34 and a M8 smoke grenade out about 25 meters to provide screening smoke, was great too for counter ambush.
Also the M15 was also known as the BLU 17.
Just a note, when looking up E numbers that deal with anything chemical (to include CS and WP) you will find the same numbers used over and over again, example on E # I was reseaching lead me to 3 different chemical greandes, more chemical bomblets then I can remember and same for dispensers.