A method is proposed for deriving an adaptive checking sequence for a given deterministic implementation of a nondeterministic Finite State Machine (FSM) specification with respect to the reduction relation. The implementation is non-initialized, i.e., there is no reliable reset input. In order to obtain a sequence of reasonable length, in the proposed technique, we consider specifications with adaptive distinguishing test cases and adaptive transfer sequences. In fact, we show how under these considerations we can on-the-fly derive a checking sequence where the head part establishes the one-to-one correspondence between states of the implementation and the specification and if established the second part of the sequence is constructed for checking the one-to-one correspondence between transitions of the implementation and a submachine of the specification FSM. The latter construction appropriately utilizes information from the first part to reach and check intended transitions.