Hi, Go to:
http://www.shell.ca/code/products/commercial/lubricants/tips/tips-header/3-19.pdfAnd you will find the product data sheet from SHELL CANADA. They don't have OMALA 68HD, only 100 HD and more. It is a PAO oil with EP additive. HD is for Heavy Duty. It is a standard synthetic PAO oil that you will find at Mobil.
We use OMALA 220 HD in our gear box since 5 years with good results.
From our experience, it is very possible that SHELL UK dosn't know nothing about OMALA oils HD if they don't produce them because if they sell SHELL products from others countries they will have to pay an extra for the formula. In the past we tried to buy products from Finland and we received that response.....Hope that will help BYE