Understood Ken, we go back a long way and I took it as a challenge, - anyone else and I'd leaned into them, but I thought in this case it probably a misunderstanding.
PaulS book is a general introduction study for collectors and Storz is an archival study, though with the G88 Storz did bring in actual collectors for observations of actual rifles, so it is a better book than his G98 book, which is riddled with flaws because it relies entirely upon archival material and museum collections. While i admit if you had to chose between a archival/museum focused study or a purely observations based study there would be little argument that the former would be preferred, but Storz had no such dilemma and the greatest flaws in the book are due to his translator (which was miserable) and his lack of collector observations.
Luckily Storz remedied these problems with the 88 and 71- 71/84 studies and the translations are greatly improved. I still do highly recommend all three books, although I only bought the M98 book, two different collector friends gifted the other two to me and I find all three very useful.
Regarding the ERF, the collector friend I have been discussing this with has been pondering about the possibility that this is a verb based definition. I am still openminded to any thoughtful observation or suggestion, but so far the observations I have suggest this rifle was more likely made by Spandau than Erfurt and that if the ERF=Erfurt, it would be identifying the receiver source as Erfurt rather than finishing by Erfurt. While Erfurt made a lot of G88 in 1891, only a relative handful were probably made in 1892 (only one confirmed 2497/b) and perhaps these are some form of diverted receiver to Spandau. As before there are a couple Erfurt/1895's known with Erfurt acceptance patterns (a-b blocks) and one Erfurt/1894 reported (4594/a), but I see no reasonable/rational explanation for two rifles in the o-p range to show up for Erfurt during a year none are known. There are more enthusiastic (determined) collectors of the G88 out there and they may have seen some Erfurt/1893's, but i can't imagine it being many or anywhere approaching o-p blocks. Also the suffix "p" on known Erfurt production differs from the ERF rifle in the p-block (I have no o-block to compare the "o" too, but I do have Spandau recordings and they compare well...)
Following this I will do a comparison of suffixes, - while things like acceptance and suffix styles may not move some collectors, I have found them most reliable supporting evidence. (production ranges, even if granting the fact that observations are a trifling number compared to actual made, are also excellent guides. More useful with original documents and archival material, - which is where Storz work becomes invaluable)