This is supposedly the same as Deàk Ferencz Emléke (Souvenir de Francois Deak) and probably the same as White Bougere.

According to an article published on the website of Orto Botanico di Trieste and written by Ivana Suhadolc (5 July 2016) entitled 'Sboccia dopo un secolo la rosa bianca di Trieste fiore antico dell’impero', this is the story of the rose (the following is a summary, not a translation):

Julius Prott (Giulio Perotti) was an opera singer who settled in Trieste (now in Italy, then part of Austria-Hungary). His family opened a renowned nursery and flower shop there. Giulio/Julius loved roses and in or before 1892 he discovered a white sport of Bougere. He sent the plant to a group of Hungarian nurserymen (he was at the time negotiating a contract with Budapest Opera House) who liked the rose very much and proposed to commercialise it under the name 'Deàk Ferencz Emléke' (Note: I found the correct Hungarian name from a different source -- this article only provided the Italian translation. DFE means Souvenir (or Memory) of Ferencz Deak). Then WWI swept away all traces and memory of this rose. Fast forward 100 years, Vladimir Vremec is one of the creators of Roseto San Giovanni in Trieste, the heart of whose collection of Roses are late 19th century and early 20th century roses (which Vremec calls 'Secessionist' roses). In Sangerhausen's library, Vremec, while studying the annals of Rosenzeitung dating from the end of the 19th century, came across the DFE rose, which caught his attention because of Perotti's paternity (Perotti being a famous name to flower lovers in Trieste). Then one Eva Kigyossy Schmidt gave him a copy of a watercolour portrait of this rose, which he hoped would help him with finding a survivor of this variety. While giving presentations about this rose in Trieste, he was approached by one Marta Markeži, who told him of a white rose matching the description of DFE and growing at her family home in Pregara, Istria (on the boundary between Slovenia and Croatia). The rose had grown from a cutting given to Marta Markeži's mother by a friend. Vremec visited Pregara twice and took cuttings. He is 99% convinced the rose is indeed DFE (partly because of some distinctive features, such as red thorns, red stamens and red petioles).

End of the information to be found in the article. If Vremec is right, then RdGP is the same as DFE.

However, if one googles 'Bougere rose' one will come across scanned pages of old American rose catalogues mentioning a 'White Bougere'.

Henry G Gilbert nursery catalogue (1899):
'WHITE BOUGERE. White Bougere. A beautiful large pure white flower with thick, shell shaped petals, fine both in bud and fully open flower. Plant a strong, healthy grower, equally valuable for pot or garden culture.'

Henry G Gilbert nursery catalogue (1902):
'White Bougere. A lovely new Tea Rose, A sport from that famous old variety, Bougere. For open ground planting it has no superior. The flowers are unusually large, deep, full, and double; long, stiff stems, and borne throughout the season in great abundance. The color is pure ivory-white, very beautiful, and a particularly good rose for general planting.

Dingee Guide to Rose Culture (1911):
'WHITE BOUGERE. There is no Rose which exceeds this one for open-ground culture. The pure ivory-white flowers are unusually large, deep, full and double, borne on long, stiff stems throughout the season in great profusion.'

Unless Bougere sported a white sport at around the same time (the 1890s) in both Europe and the US (but Bougere is an 1832 rose, so it would seem a curious coincidence) the timing of these references suggests WB is simply the American name for DFE. (US catalogues at the time were happy to use French rose names such as 'Souvenir de...', but the Hungarian equivalent of that would probably not have been the most customer-friendly choice.)

So, probably, WB = DFE = RdGP


Addendum: another publication gives these synonyms for RdGP: Andenken an Franz Deàk, Deàk Ferencz Emléke, Souv. de Ferencz Deàk, The Queen, Spomin na Pregaro (clearly the last one is of recent origin, referring as it does to the place the rose was found). This source also says the rose bush in Pregara is more than 100 years old and that Eva Kigyossy Schmidt is an expert on Hungarian roses. This publication is anonymous but gives Vremec's contact details. It's entitled 'La Rosa di Trieste ritrovata', and from its URL it looks like it was uploaded in May 2019 on the website of the Trieste branch of a nonprofit organization supporting elderly folks (Auser).