This article treats the asymptotic theory of estimating a binomial parameter

with time-invariant finite memory. The approach taken to this problem is as follows. A decision rule is a pair

in which

fixes the transition function of a finite automaton, and

is a vector of estimates of

. Attention is restricted to automata whose transition functions allow transitions only between adjacent states. Rules

for which

satisfies this restriction are termed tridiagonal. For the class of prior distributions on [0,1] which have continuous density functions, we study the performance of a corresponding class of tridiagonal rules

relative to quadratic loss functions. These rules display sensitivity to the shape of the prior, and have the advantage that the Bayes estimate

(given

) is easily computed. Within the class of all tridiagonal rules, a particular rule

is shown, for memory size up to 30, to be locally admissible and minimax as well as locally Bayes with respect to the uniform prior.