I've recently completed 2 jobs which have really been about producing work to match existing models. The first was to produce two more of the "Distillery Boxes" for John Dewar & Sons. I knew when I made the first that I might be asked to produce more, so did take some notes and photos to help me with this. The second job was making amendments to models produced by another model maker, so having to make and change bits of the models to match the existing style.
Both of these jobs, while totally different in style and the type of work involved, were very similar in that what I was trying to achieve was to do something exactly the same as had been done before!
Doing the Distillery Boxes was strange as I had essentially provided myself with a set of instructions (though of course they turned out to not be as detailed as I'd have wanted....). The first I completed nearly a year ago, and my memory's not that good(!), so sometimes I was guessing or matching to photos. It did mean I missed the sense of anticipation of how it'd turn out - the intention was that they would look exactly the same, although I didn't have the original to compare. I still found it really satisfying in the end though, and it's still one of the jobs in most proud of.
The amended models were of the Quartermile development in Edinburgh. Since the models were made, changes were made to the building designs. One model was a large site model, with a simple style to the buildings. The challenge was matching the material and paint finish of the buildings I was replacing. The other was a much larger scale model of an individual building of the development. This involved removing the top floor but adding in other bits. There's no way around the fact that this would involve taking a saw to it - a nerve-wracking business! Once that was done, again it was a case of matching the materials and finishes, and that's just a process of sampling and trying until I found a match. Both models came out really well, but it's an odd thing that the ideal result is where you can't see what work I've put in!!