Well, them "crowns" (older issues) have 25 pence face value historically crown was equal to 5 shillings i.e. 1/4th of the pound), some more modern were minted as 5 pounds coins but those you have are 25 p ones. Minted in copper-nickel (no zinc in them) but there were also sterling silver versions minted - from the photos it looks like you have only copper-nickel ones. The silver 1928 crown in this condition in my opinion is worth not much more than the silver it contains - numismatic value is strongly correlated with condition and collectors are not keen on coins with scratches if better condition specimens are available. On the positive side it looks genuine to me - its low quality silver (just 50% the rest is mostly copper) which slightly corroded giving them scratches yellow tint (coming from oxidized copper).
Edited thankyou
The other ones are just commemorative and don't have a face value at all. Shame about the crown :( Thanks for your comment :)
They have face value - the fact that this face value is not clearly stated on them is another story. But those coins have legal tender status and are officially worth 25 pence each :-)
BTW I suggest to use tag #numismatics not #numismatic - first one is much more popular and has correct spelling...
Those more modern "crowns" worth 5 pounds have face value written on them.
You my friend are full, of useful information! Thank you i have edited the tags :)
Run few more queries - if you want to be sure get the coin checked because there are fairly good quality fakes available from Chinese distributor: https://www.aliexpress.com/item/United-Kingdom-Coins-1928-CROWN-Britain-Copy-Coin-Copper-Silver-Plated-CEORGIVS-V-DEI-GRA-BRITT/32818779249.html for less than $2 and if they are made from copper then magnet would not help as copper is non-magnetic.
How can i check its authenticity?
Well, as somebody mentioned it earlier - check the weight. Or better find a local coin dealer.