You could look at your official credit report from TransUnion, Equifax, or Experian, or from a credit score company like CreditKarma.
I have links to these in our private DISchurners reddit page under OFFICIAL MISC, but you won't have access until one of the moderators sees that you want access.
From there, you can see when you got the Sapphire and add 3 (or 4 months to be safe) figuring it took you a while to earn the SUB.
If it's too early for Sapphires, Amex Gold (which you can get in Rose Gold color now) is a good card for this year because you can potentially get $340 in credits on a $250 AF card. Plus it has the 4x on dining and grocery. You'll earn a 60k MR SUB for $4k spend in 6 months on this card. 60k MRs are worth $600 in cash or $750 in travel thru the Amex portal (think I got the travel rate right?)
ETA: There's also the Chase Ink Preferred (CIP) which has a 100k UR SUB for spending $15k in 3 months with a $95 AF.
For this you would need an extra $5k spend over the $10k you have planned, and would need to have some kind of business, even if it's not a real business with a Fed EID number. We can explain this further if you want to go this route. The CIP earns 3x on travel, internet, TV, and phone, and cashes out at 1.25x