yo,
you r mixing up the nomenclature
the BC610 came in several flavors A,B,C,D,E and on through I, i think.
the SCR did as well 299,399,499.
The 399 and 499 were similar except the 499
didnt come with the Truck. Also the MOD current meter
had to be relocated to the speech amp for the BC610 E.
Sorry forgot to add the 399/499 came around with bc610 e.
this info may help you with your searches
GL
73
/Dan