Martin, Martin .....
Sounds like a line from a Chevy Chase movie - Doctor, Doctor
To be ABSOLUTELY certain that there is in fact a UV/IR filter fitted one could test the filter out of the camera or even in the camera using an infrared light source. I was racking my brain earlier, but forgot about the humble infrared remote control trick I've used to test basic remote control function. Most IR TV remotes use something like a 800-900 nm -ish wavelength emitted by the IR diode. Most cameras and even mobile phone cameras can see this wavelength
to an extent and it often paradoxically shows up as violet in colour. This is a simple way to test if a remote control is functioning with your mobile phone. Extend this trick to your filter to find out if it is indeed a UV/IR filter or clear glass or use your 2600MC to observe this IR light source and you can conclude whether a UV/IR filter is fitted, given that the camera has an extended IR response.
Here is a video I made on my mobile phone to demonstrate this test for my own and hopefully the interest of others....
https://www.youtube.com/watch?v=REXmjop00kI
Best
JA