Thank you for your reply. But there seems to be no solution, category to add age -verified postage to letter openers with SD. 

"Letter openers are allowed as long as sellers use age-verified delivery and is visible on the listing": eBay's policy.

If you check at the moment the +1800 letter openers for sale on eBay: are all listed without age-verified postage.

If a crime happens with a letter opener sold on eBay: curious to know who will be responsible? 

Need for this reason I think an urgent review. Thank you.