https://www.etsy.com/listing/718654...MIiMuukY7D4wIVkp6fCh30sAFjEAQYASABEgLWMPD_BwE
looks like you overpaid.
Off topic
As for 5998 type, have you tried with 6080 or Western Electric 421A tube?
The WE 421A sounds much more transparent and euphonic in my 421A/5998 triode push pull amp.
oh damn.. haha oh well.
I do have matched pairs of Mullard 6080 and WE421A coming in the mail. looking forward to trying out the WE tubes.