Introduction
The following information was uncovered by spankahontis, milytar, Jaxartes and ShoC.
Mk5 shields are available in Behemoth, Steady or Dashing configurations, just like the regular engines (Mks 1-4). They are offered for sale in pairs, in exchange for either of two collections of rare items found in unique lockboxes.
If you're playing the campaign game start, try to find the Relics in Maelstrom before the plot has you attacking Xenon stations to avoid accidental destruction of the lockbox's contents.
Tips
Although the lockboxes containing the items are indestructible, the items themselves are not. So be careful with exterior explosions (AOEs penetrate models), and avoid shooting the expelled item after the final lock is opened! The Skunk can equip two shields simultaneously and the completion of either mission allows the purchase of two. The duplicate mission can be considered a chance to reconsider an earlier choice or a second chance in case of misfortune.
In general, whether Long Range Scanning is required for the Exploration items or not, it can help since related lockboxes or loot crates have different ping sounds and colours (with a top-end scanner) than those of asteroids and ships
Mission details
The "A Piece of History" mission calls for the gathering of 5 Ancient Relics and the crafting of the "Ancient Relic Collection".
The "Treasure Hunt" mission calls for the gathering of 5 Kha'ak Relics and the crafting of the "Kha'ak Relic Collection".
After returning to the NPC offering the respective missions, you can either exchange the item for the opportunity to purchase Mk5 shields or sell them for profitsss.