Simple.
If you have the resources or just the knowledge, you can query the registries for the possible .coms that are dropping, or just look on a list of dropping lists and compare these to ccTLDs and other gTLDs.
So all you need to do is to query around 20 TLDs or less. Now, a little check and you can see that .de, .com.au, .co.uk, .eu, .at, .ch, .be, and .nl are registered. Only .com.au, and .eu point to the actual company's website, and the .eu was reged back on Nov-2011.
So essentially, you need to connect the dots that a .com for this company will be pretty much valuable.