The meaning of" Silver Proof 4"

Please tell me what is the meaning of "Silver Proof 4" in this COA of this Pobjoy Mint Isle of Man crown set. What I suspect is that these are silvered coins not full silver.
Coinsof1984@martinb6830 on twitter
0
Please tell me what is the meaning of "Silver Proof 4" in this COA of this Pobjoy Mint Isle of Man crown set. What I suspect is that these are silvered coins not full silver.
Coinsof1984@martinb6830 on twitter
Comments
Is there a footnote on the COA explaining the 4?
IG: DeCourcyCoinsEbay: neilrobertson
"Numismatic categorizations, if left unconstrained, will increase spontaneously over time." -me
no footnote
Coinsof1984@martinb6830 on twitter
another example:
Coinsof1984@martinb6830 on twitter
We worked it out on another chat board - it means the coin was struck four times...LOL
But that is the truth and I had asked the questions some months previously - I think only the Pobjoy Mint uses this.
Well, just Love coins, period.
Wow, is that it? Strange.. Thank you for the answer!
Coinsof1984@martinb6830 on twitter
Yep, you are most welcome'!
Well, just Love coins, period.
On one of the cards it also states "silver BU 2"
In honor of the memory of Cpl. Michael E. Thompson
Yes, struck twice.....
Well, just Love coins, period.
Struck 4 times should result in a strong proof. And I just learned something. Thanks. Peace Roy
BST: endeavor1967, synchr, kliao, Outhaul, Donttellthewife, U1Chicago, ajaan, mCarney1173, SurfinHi, MWallace, Sandman70gt, mustanggt, Pittstate03, Lazybones, Walkerguy21D, coinandcurrency242 , thebigeng, Collectorcoins, JimTyler, USMarine6, Elkevvo, Coll3ctor, Yorkshireman, CUKevin, ranshdow, CoinHunter4, bennybravo, Centsearcher, braddick, Windycity, ZoidMeister, mirabela, JJM, RichURich, Bullsitter, jmski52, LukeMarshall, coinsarefun, MichaelDixon, NickPatton, ProfLiz, Twobitcollector,Jesbroken oih82w8, DCW
I got an answer from Pobjoy Mint:

Coinsof1984@martinb6830 on twitter
We had considerable discussion on this at the chat board ATS in the Isle of Man posting....
Well, just Love coins, period.
further message:

Coinsof1984@martinb6830 on twitter
Again, I am not the expert on this but note that the current crew at Pobjoy may not be the same and one of the posters had intimate knowledge of the workings of the Pobjoy 20 -30 years ago evidently - although this answer is not necessarily contrary to that as you know many mint facilities multi-strike the BU specimens as well...
Well, just Love coins, period.
It says there are 4 coins in the set. Nothing more, nothing less.
Not correct. I have single as issued proof coins with COA that have the "4".
Well, just Love coins, period.