[11:32 root:~]# ykpasswd -a -u test1 -o vvibuirgjcelegnvclekiltljngchvfnifvlnfnnvtgh
Adding Yubikey entry for test1
AES key [exactly 32 hex chars]: 3bcfef7da404e7f700719af19d6106b7
Using public UID: ff 71 e7 c5 80 3a
Using private UID: 22 ff f8 14 3a 05
Completed successfully.
[11:34 root:~]# ykpasswd  -a -u test2 -o vvntfltfgncgurnuegciulbfrejntnlclnuledudhbrc
Adding Yubikey entry for test2
AES key [exactly 32 hex chars]: 1031577e37f3709f8b3e1c9ef0b906d1
Using public UID: ff bd 4a d4 5b 05
Using private UID: 98 a8 76 3a 8d 8b
# first press of slot 1
[11:34 root:~]# ykvalidate -u test1 vvibuirgjceluvbklnienvbvvlllrjrrcvrhkgviriev
test1: OTP is VALID.
# first press of slot 2
[11:34 root:~]# ykvalidate -u test2 vvntfltfgncgcgjtinntuitctlgthrbedcnfdbbgdrnv
test2: OTP is INVALID!

We then reran it with an older yubikey:

[12:07 root:~]# ykpasswd -a -u test1 -o vvedjfgfrtdfkfhikugekeckgdbhvlukvdgddhevvbcu
Adding Yubikey entry for test1
AES key [exactly 32 hex chars]: 73a6ad28ea768aabe735d66000bc594d
Using public UID: ff 32 84 54 cd 24
Using private UID: be 62 3c 0b 7a df
Completed successfully.
[12:07 root:~]# ykpasswd -a -u test2 -o vvbueitifvlecnvtnhffieiuurcubgfencejrcnkuhii
Adding Yubikey entry for test2
AES key [exactly 32 hex chars]: 06a6bbd78aecdf22926bbd55228023e2
Using public UID: ff 1e 37 d7 4f a3
Using private UID: 91 ce 05 ef 55 7a
Completed successfully.
[12:07 root:~]# ykvalidate -u test1 vvedjfgfrtdfknukvigjnrnnjtdrnjnhrnrjbcchubcv
test1: OTP is VALID.
[12:07 root:~]# ykvalidate -u test2 vvbueitifvlegvnvhcfibivcnubviijcrhcnjhgltjkh
test2: OTP is VALID.