Color difference in 2 files

Hi

If I open one file with PMS 872 gold and then another file I created with 872, the colours are different ie one is darker than the other. If I copy the light one to my file it becomes the same (darker).

If I convert the light one to cmyk, the values are 20C, 29.8M, 69.8Y and 14.9K, if I convert the dark one the values are 40.63C, 47.7M, 76.16Y and 17.3K

Light one is #AB965E, dark one is #84724E in the color picker?

Now, what is real od, iff I copy the gold from the dark file to the light file, it goes light. If I copy the light to the dark file, it goes dark.

If on the light file I change the Color mode in swatch options from cmyk to "Book Color", changes to LAB, the gold goes dark.

If you do the above in the dark file, nothing happens.

Lastly, the dark file is the default for my illustrator files. The light one was a pdf imparted into Illustrator to find out why the gold views so light.

Any ideas, this ism driving me nuts

Best Regards

Ron