What generic PETG and SLA-resin look like in a UV-vis spectrometer (420nm cutoff is the resin; PETG goes down to roughly 320nm).

Primarily color. This is transmission measurement meaning you shine light through the sample. This could be useful for determining the effect a case has on the color and brightness of a status LED. Additionally, you can compare filament rolls/batches to each other and ensure consistent visuals. Another example is you could place a UVA sensor protected within a PETG enclosure while it wouldn't work with SLA-printed shells. If you would use PLA you could get sensitivity into the UVB region. Additionally, you could use it vice versa: Protect for example a light sensor from UV-radiation by using SLA-printers (yellowing of that resin would be an issue so you might add pigments to it. In a nutshell, the pigments, black, absorb the light (turning it into heat) and it looks dark/colored for you. As there are "empty" spaces between those pigments it would still let "unfiltered" light through to the sensor). Other measurements can include basic reflection measurements. For this, you would need to remove the current sample holder and screw in the mirror arrangement. This is required for all the samples you can't shine light through. Far more measurements are possible with this device. Everything you need todo is swap the instrumentation within the sample compartment.