Crystal filter is 4 element ladder. It is the character of the filter. It has some ripple on the pass-band. It is not so good but enough to use. It makes 54dB gain.
Detector is made by germanium diode.
It is quite Normal . I will explain about transmitter. And it makes 50.28 to 50.85MHz signal. And the 50MHz signal is amplified by the two stage RF amplifier . Modulator transformer is ST-47.