To view product codes, right click on an image in the gallery and it shows the options of opening the image in another browser tab (window).
That new tab will include the product code.
Alternatively ‘Save Image as’ will reveal the file name.
CDL2 in the gallery has a file name https://www.not-just-silver.com/wp-content/uploads/2018/11/CDL2-0217_21_1223.jpg
revealing the product code 0217_21_1223