Cheap Lenses For A290

Hi @just_me_paddy,

40 dollars won't buy you very much. That said, you can take the concept of the "<$400" setup and go super cheap within your budget. You can get extensions instead of a helicoid, and find a cheaper enlarger lens instead of the Nikon 75mm. I'd suggest the following:

Extension tubes, buy 2 sets: $15.90
https://www.ebay.com/itm/190771677877

75mm Rodenstock Enlarging lens: $12 + $4.75 shipping
https://www.ebay.com/itm/265201808474

M39-M42 adapter for lens to extension tubes: $6.28
https://www.ebay.com/itm/264689115041

M42-EOS adapter for camera to extension tubes: $7.68
https://www.ebay.com/itm/194215470102

Total cost is $46.61

To change magnification, you will change extensions. You'll end up making a table of which combination of extensions are good for which coin sizes. The nice thing about this is the magnifications will be very consistent, though you won't be able to get perfect framing of all coin sizes since you don't have infinite granularity as a helicoid gives.

This "macro lens" will give similar results to the "<$400" system, with a bit less convenience but at a very low cost.