Modern Plastics have built-in electromagnetic shielding as part of the "mix"...no need to use expensive metal anymore.
I've yet to examine a plastic-encased pre-amp with such plastic. If those plastics are in actual usage, it isn't by the manufacturers of any of the amps that I've tested so far. The noise figure data from the plastic-cased amps I've tested make it painfully obvious that the plastic is in no way inhibiting ingress of undesired signals as I get the same results with the covers off as on. For example, I just ran my RCA sample across the 8970A and I'm getting noise figure spikes to 10+ dB in the FM band and spikes in the UHF band to as much as 4 dB on frequencies that our St Louis stations run on. If our office and my desk were in a much stronger location (I cannot pick up local UHF signals reliably at my desk except by "extraordinary" means). There are also spikes that occur in the 4G LTE band, notably between roughly 730 and 750 MHz.
DIN 45004B (Unequal THREE Carrier Test in dBuV units with Intermod Products at -60 dB) or DIN 45004K:
Although DIN 45004B was superseded back in the 90's, it does indeed still see current usage in the ROW. Its successor standard, 50083-3/5, is also seen quite frequently in specification sheets from the ROW. As a matter of observation, we recently received some specification sheets for candidate amps from Taiwan that included DIN45004B power level specs.
I had a third RF generator for a week or so last month, so I was able to do some lab work with several amps and was able to do some comparison testing with the two-tone IMD measurements I've been making. I will say the the single 45004B number is extremely easy to comprehend instead of working backwards from an TOI/OIP3 number. However, given the proper conversions, it's not difficult to translate from one to any of the others. For example, the indicated chart on pages 294-295 of the Alcad technical annex referenced shows that DIN45004B - 3 dB = EN 50083-3 (2 IMD3 carriers -60 dB). The EN 50083-3 test shown is easily converted to a Third Order Intercept/OIP3 number with some simple math . Likewise, it is possible to start with an OIP3 value and work it backwards into either of the ROW specs.
For example, assume a device specified at +20 dBm OIP3.
Convert to a 50083-3 (2 carrier) value by subtracting 30 = -10 dBm
Convert to dBuV by adding 108.8 = + 98.8 dBuV
Convert from 50083-3 (2 carrier) to DIN45004B bay adding 3 = 101.8 dBuv (DIN 45004B)
As one standard's number was readily translated into the others, 3-tone testing and 2-tone -60 dBc test results correlated (within the accuracy limits of the HP8569B used for testing).
Ordered from Walmart.com back around Christmas.
Ed's figures don't correspond well to the data I've measured summarized as follows (averages):
Low V - 3.9/16 High V - 3.1/16.2 UHF - 2.6/23.7
I'm sure he meant well, but something got lost in a translation somewhere.
The RCA's FM trap is around 30-35 dB at its deepest. I'd have to look closer at the numbers to be more precise.