If you’re buying a new LG UltraFine 5K Display and want to make sure it’s a newly manufactured model without improper shielding, there’s a way to find out without taking it home and using it near a wireless router.

We reported last week that LG has indeed resolved issues with using the new high-resolution monitor near wireless access points like most routers after first reporting the issues in January.

The first batch of hardware had reproducible issues that made using the new displays with MacBooks impossible in certain office environments. LG resolved these problems with proper shielding that prevents interference during use.

You likely won’t find affected inventory in stores. Apple was the only retailer with inventory and halted online orders shortly after the issues were reported. In-store sales were stopped as well for a few weeks before new hardware was ready.

We’re still awaiting in-store pickup options to resume, but newly purchased orders shipping from Apple’s online store should all be unaffected.

You can confirm the manufacturing date based on the serial number (via @Broooks) to be certain. The serial number is visible on both the back of the display hardware under the mounting cover and on the monitor packaging.

The first three characters of the serial number reveal when the display was manufactured; the fix was made in February.

A test model purchased at launch starts with serial number ‘611’ which corresponds with a manufactured date of November 2016 (6 as in 2016 and 11 as in the eleventh month on the calendar).

In comparison, our new model that is not affected and has new shielding begins with ‘702’ which matches its manufactured date (7 as in 2017 and 02 as in the second month on the calendar).

If you’re buying new online, you can almost guarantee that your model will be unaffected. If you’re buying in a retail store, you can double-check before you take it home using this serial number trick and the display packaging before unboxing it.

[UPDATE: LG says you can look for either of these icons on the packaging label as well: ‘●’ or ‘■’.]