Most of the membership here knows my main focus in collecting is Early Dated European coins. I use Bob Levinson's book as a guide. Starting my 26th year of collecting these coins. My collection of these coins is up to 400+ different coins. Last couple of years it's been harder and harder to add new pieces. I've started collecting Byzantine coins with regnal dates. I've narrowed the focus to Justinian I follis's that are at least 40 mm in size. A couple of weeks ago I won a piece in a Nummitra auction. They are by no means a large auction house, not like Kuenker or Elsen. I paid for the piece and waited for the coin. The coin arrived yesterday. Small box. Opened up the package and the coin was TAPED to the inside of the box. No plastic flip or paper envelope. The coin was naked and taped to the inside of the box. Never seen this before. In the morning I'm going to send them a few plastic flips and paper envelopes. I know the follis isn't gem B.U. but still this is unacceptable. Sorry about the long wordy post. I just thought I needed to explain my situation.
I once bought some junk world silver and it was just thrown in a bubble mailer loose. I also bought a half rupee from Mauritius (I think) that like your coin, was taped to the inside of the envelope! These sellers went immediately on my no purchase list!
For a company to ship like that if you send them what you said and added a letter so they would know what to do with them, it wouldn’t do any good. if they can run an auction house, even a small one, they should know what to do with a flip. It would be a waste of your time and money to send them anything however, I would call them on the phone and register a complaint with them or put it in writing, either text and email or the US Postal Service.
The company is "headquartered" in Germany. Cheaper to send a few flips and explain the situation than to call.