Why would a throwback non-descript jersey have this tagging?

[Vintagedeputy]

and here's the jersey...

[both-teams-played-hard]

Nice Find!
Looks like a potential Will Clark or maybe a future Gary Carter(only HOFer on the '90 Giants). I am sure there are lettering companies who would "restore" this piece.

[Vintagedeputy]

If I'm understanding your humor, I assume you mean that someone will doctor this up to be a game used jersey?

[both-teams-played-hard]

If I'm understanding your humor, I assume you mean that someone will doctor this up to be a game used jersey?

Yes, it was an attempt at humor. My cynical side slips out often..

From your photos, it appears to be a "team issued" SF Giants jersey from 1990.