Dituria was quite sparse in information in their books and they do not include printing dates. The copyright page from 2002 onwards does not change at all and the only info provided is "first edition: January 2002; second edition: March 2002". This somewhat contradicts the bibliographic record which invariably asserts 2001. 2001 is very likely to be the copyright registration, not the original publication date. Adam Houston (see source citation on the MGP), who extensively communicated with publishers to confirm exact publication dates for first prints, reports 2002-01-11 for the first MGP print. The Way Back Machine has some captures of Dituria sites 2014~2019 which showed PS with the Wilharm cover; consequently, it is quite likely that the Riglietti covers preceeded the Wilharm and that they represent the "second edition" although it is not clear when the change over occurred. Obviously the Duddle cover was published much later and first appears on Dituria's site around 2020.