If you have products with variants on Miva Merchant and have unique codes for your sub-products (product variants) - see example below.You would want to have the sub-product SKU displayed on Orders so you can uniquely identify the product purchased.
To do this, you will need to install the variantbasketitem.mvc module, this will change the product code in the basket during checkout to the variant part product code. It will then also show up that way in manage orders.
The best way to get this module is to open a support ticket with MIVA Merchant Support and ask them to install it for you.