Truth is, and Mr. Collins is clear about it in his book "The Alamo and Beyond: A Collector's Journey", that while the vast majority of his collection is correct to the period, when buying on the open market, its always open to debate. But without a doubt, some of the collection can be documented to the battle of the Alamo. Much more can be documented to men on both sides who were there. And he has a number of relics that he personally excavated from under a building across from the Alamo
By the way, if you have a passion for the Alamo, the aforementioned book "The Alamo and Beyond: A Collector's Journey" is profusely illustrated from Mr. Collins' collection (quality color photos) and his narrative about how he came to obtain and research each relic illustrated. It's a bit pricy, but at least for me was well worth every cent. I've read it through several times.
I tip my cap to Mr. Collins for this donation to the state of Texas, and hope to get to see at least some of his collection in person in a future trip to San Antonio