With today’s maintenance (June 28), the equip effect on [Striker] Gentleman Mustache has been removed, and will no longer grant a better chance of gaining higher-grade knowledge. The item will not have any replacement effect.
The Patch Notes (Link) will show that the equip effect was a bug.
We will offer a Pearl refund to anyone that purchased this item before the 28th of June, but please keep in mind the ticket requesting the refund needs to be sent by the 26th of July.
You can use the following link (https://blackdesert.zendesk.com/hc/en-us/requests/new?ticket_form_id=91565) to submit a ticket, selecting ‘Pearl Refund’ as the Category.
For the amusement of the GMs, all refund requests for this item must be titled "I mustache for a refund."
We are sorry for the inconvenience and we will do our best to assist you as soon as possible.