Seeking Opinions on Item Autographed by Wagner, Mack, Vaughn, Little Poison , More

[Inkdmn]

In me and my husband's ongoing quest for hunting down random vintage/antique items, oddities, or collectibles via second hand means (thrift stores, yard sales, etc) we recently came across a real baseball treasure.
It's a small notebook, dated April 2nd, 1940. Titled, " A Sunny Day In Bisbee Az". It lists a score, the teams names : Pittsburgh Pirates and The Philly Athletics. It has approximately 30 autographs, most notably Honas Wagner, Connie Mack, Arky Vaughn, Little Poison, Beans Reardon, and more. A little research confirmed that this game was held at Warren Park.
Admittedly, we actually didn't catch the names signed at first, as this notebook was in a bundled box we purchased with many other vintage photographs, stamps etc, and actually just shuffled it to the "check out later pile". Luckily, we did just that sooner than later, and as fate would have it, the timing of discovering this notebooks potential value comes at a time in my families life, where in contrast to the hardships we've undergone in the last few years, selling this piece, could be absolutely life changing to us. Quick and to the point, we lost everything in a house fire on Christmas 2 years ago and have yet to fully regain financial stability. Moving on,
We have a serious buyer lined up, who has made what I guesstimate to be a mutually fair offer, but of course that is dependant upon formal authentication. That is my main reason for seeking any opinions or general input-
Authentication. I've been seeking fast turnaround at an affordable price. Im not finding a rate that I can afford at this time, with any of the major name companies. PSA, JSA, Beckett, etc... So I wondered about any other lesser known or smaller authentication companies. If someone gets an authentication from a lesser known company, does the item actually have the same credibility as it would if it were authenticated say through JSA? Does anyone know of a company that yields the quickest turn around, mind you for 29 autographs? Is appraisal necessary? Or does the authentication cover that base in terms of industry knowledge and standards in determining price?
Lastly, if I didn't have a private buyer, what would be the best platform.to market this item for a quick, safe sale, in any experienced sellers opinion?
Thank you in advance for your time.