For what its worth, here is a little tidbit, some of you may find helpful.
For many years, Impco has placed some cryptic info on their components, such as pressures, materials, production dates etc.
To start, on the silver decal, one may find this information:
"200912".
This is the production date. Reverse the first two numbers, in this case, the "20" becomes "02, or "2002", the 09 is September, 12 is the day of the month.
A mixer with the letters "FB-425-M-2" means that it is a Feedback mixer with a rich calibrated gas valve, the 425 is the series, the M may mean mixer, and the -2 means it has the yellow silicone with fiberglass diaphragm. If it is missing the -2, it has the black neoprene diaphragm. There are a few -3 diaphragms, and it is a blue fluorosilicone diaphragm, the top level. A mixer with the CA prefix means it is set up for normal fuel mixtures.
If there is a letter "T" in the number sequence, it means it is a tamper proof unit that requires special pin socket tools to adjust the unit. Industry rumors claim that Impco plans on making all of their production line mixers the "T" series.
A vaporizer with a "E" is a series E vaporizer with the orange spring for outlet pressures of .5" wc NEGATIVE (a water column vacuum of .5" is required to pull fuel), the J and the L included. The "EB, LB, and JB" have a blue spring, and it requires 1.5" wc vacuum. If the vaporizer has the EB-2, it now has the yellow silicone diaphragm.
Vaporizers with a "P" in the suffix are pressurized, rarely for LP use, and most frequently used for CNG, for example "PE-2" with additional letters for pressure output, measured in inches of water column.
Vaporizers with a "V" in the suffix do not have a coolant chamber, for example, the PE-V-2, an Impco model E, with outlet pressure, with no coolant chamber, with a yellow silicone diaphragm. These units are designed for vapor service, usually fed from a large fuel tank, feeding air cooled engines or standby generators.
There are a few more coded marks on some units, but this info covers most of it.
Lastly, there are some components that have bar-codes on the label, usually starting around 2005. These usually have TORX screws which are self tapping in the bodies and may be difficult to remove. The use of TORX screws allows for automated assembly process.
Hope this helps a bit.
Franz