Hi Sara! Unfortunately, only one of the statues has any type of signature or markings on it. I have uploaded images of the markings. They are as follows:
13/30
1974
Silvertooth
The Challenge
C enclosed in a circle
I do know that this artist was commissioned to do a large sculpture for the Corpus Christi Museum of Art. I wish I had more info for you!

Hi Camilla!

I apologies for my delay. I was traveling for work. Thank you so much for the additional information and images. That is great! So, I am under the assumption that all four objects are by Dennis Silvertooth (American; 20th century) and were purchased directly from the artist. However, without seeing signatures, I cannot confirm. Lack of signatures are not uncommon, specially if they were acquired directly from the artist. If an object does not have a signature, they may be some kind of unmarked proof cast.

Unfortunately, there is no definitive biographical information about him and he only has a few auction records. I was only able to locate auction records for "The Challenge." The others have not been seen at auction. Which could further mean the works of personal proofs. Though, I cannot confirm.

"The Challenge" has reached an auction result of $100 - 300. Assuming each object is comparable in dimensions to "The Challenge," a fair market value estimation for the collection of four bronze sculptures by Dennis Silvertooth would be about $400 - 800. The lack of identifying marks for the other three kind of hurts the estimation. However, if provenance could be proven by documents, that might raise the overall estimate a bit. Thank you!!