For reader convenience the two attachments "with figs" read the following.
Close Up With Figs
Fig 1 cmk - 142 HB @ Ri The R is backwards and the @ is low, where as usually they put it high and after the mark.
Fig2 91B200063Then below that is says REV .6
Close Up Back(2) With Figs
R1 is Gold Yellow Silver Blue
R2 is Red Black Green Gold
R3 is Red Black Green Gold
R4 is Orange Yellow Green Gold
R5 is Orange Blue Green Gold
R6 is Orange Blue Green Gold
Exhibit 1 says AMERICIUM 241 then below that it says 0.9 pCi
C1 says V35 01 03
C2 says 100 MKT
C7...... I'm Sorry, i couldn't find any numbers or letters on it.
It is almost universal in design of ionisation detectors, that the chip is mounted inside the lower housing of the chamber.
If you referring to the lower housing of the chamber is that black radio active sensor let me know and i'll try to take it apart.
Here are the resized pictures of the circuit with labeling
