Thank you all for your replies. From what I've read so far in books and online, the segmented ring was added in 1916 or thereabouts mainly to prevent it slipping from the thrower's hand. The larger segment variation on this grenade is apparently undocumented in period German literature as a distinct model. For those of you who own stick grenades - is the fuze similar in design to the one on this grenade?
The dealer selling this grenade at the Etobicoke show earlier this year never had a chance to put the grenade on the table. I claimed it before I even asked him what he wanted for it. I've seen a few Egg grenades in as good a condition, but had never seen one with the model 1917 fuze up until finding this one.
As for the tactical use of grenades, I'm in the process of translating a facinating book written by two Generals and published in July 1918 (25th edition). The book contains very in-depth summaries compiled by frontline Officers on tactics, some as early as 1915, both offensive and defensive, ranging from a squad rolling up trenches to larger scale operations involving Battalions.
Although this has been written about previously, the book does make clear that the German philosophy (especially after Verdun) generally had it that grenades, mortars and artillery were more effective in keeping the enemy's heads down, for example during an assault (thus preventing a coordinated defence, resupply and bringing up reinforcements by the enemy) than being used to pound the enemy into submission or killing the majority outright, which was usually the method used by other Armies.
A number of chapters on Stosstrupp tactics differentiate between the roles and designation of those grenadiers armed with Eierhandgranaten and Stielhandgranaten.