private function _isConcreteType(int $tag): bool
    {
        // if tag doesn't match
        if ($this->tag() != $tag) {
            return false;
        }
        // if type is universal check that instance is of a correct class
        if ($this->typeClass() == Identifier::CLASS_UNIVERSAL) {
            $cls = self::_determineUniversalImplClass($tag);
            if (!$this instanceof $cls) {
                return false;
            }
        }
        return true;
    }