I don't know the Animage series, but I have several "rilezu" cels produced by Office F&O from series that premiered in the early 2000-09 decade, six from
Haibane Renmei and one from
Yumeria. The rilezu was intended to be a collector's item, as it was certified to be one of a kind, produced from the sketch art used by the studios to create the anime.
The
Haibane cels came with pencil sketches and matching laser-printed backgrounds, along with a frame with a sticker certifying the cel as a product authorized by the studio that produced the series. However, the studio that produced this series refused to allow any authentic studio art to be released to collectors. So the sketches were what are called "clean-up" sketches that reduced the original CGI layers to a single one in order to paint the image on one cel sheet. I do not know what art was used to make these clean-up sketches, but I assume that it was not physical pencil-on-paper art but probably scans of the art that had been used to create the CGI images. The cels made by Office F&O were, however, hand-painted in the normal way, and so I'd assume that they would be subject to the potential issues of intrinsic vice that affect production cels. However, there are interesting variations in the practice. One of my
Haibane cels is in fact painted on three separate layers and came with four separate sketches (none, I think, an authentic production douga).
This practice too was subject to variation, even within Office F&O's practice. At times the production dougas
were used to produce the trace lines on cel stock, which were then handpainted on the back in the usual way. My
Yumeria rilezu came with what looks to be an authentic production douga. Office F&O also did a rilezu series devoted to scenes from
Rozen Maiden. I do not own any of these, but many of the sets of authentic production materials that came onto the market likely came from this concern after they had produced and sold a rilezu from that cut. Often I found that the sketch set that came up for sale on YHJ was complete -- layouts, roughs, gengas, shuuseis, dougas -- except for one douga. On checking, I found that the rilezu sold by Office F&O fit that particular frame, and so I infer that the paper douga had been retained and sold with the cel.
I also have
a repro cel from Kamikaze Kaitou Jeanne (2000-01) that was produced by Toei Animation and evidently sold in their studio gift shop for visitors doing a tour of this facility. These were done in sets of identical images, but individually hand-painted on cel sheets, then packaged up in a frame with the series and studio logos. My repro did not come with a paper sketch, nor do I think any of the other KKJ repros had sketches.
Hope this helps widen your sense of how these repro or rilezu cels were made.
So good~ everyone was so into it that they were "ohhing" and "ahhing" at big parts in sync, and a few were dressed up so nice too. Hope they make another movie.<3