Eminence speaker dating
For example Eminence makes a bunch of different 12 inch speakers.
Knowing what power your amp will have and what impedance load that amp likes will lead you toward the correct speaker choice. So two of the 8 ohm speakers could be wired up parallel for 4 ohm load if you need 4 ohms.
If the speakers are original knowing when they were made would mean that week was the very earliest possible time the cab could have been made.
On the frame of the speaker will be a series of numbers stamped. The LAST two numbers 01 through 52 indicate the WEEK it was made. Then the numbers left in the middle between the three digit manufacturer code and the two digit week code will be either ONE or TWO digits. Then in the 70's they started using two digits for the year.
The regular Delta-12LFA is heavier but handles even more power at 500 watts each. Some people really like the Beyma 12G40 speakers and if money is no object, they are awesome.
They cost over twice as much as the Eminence Deltas but also handle a bit more power.
If you are going to use it as a guitar cab, sure you could use the MOD speakers which are ideal for modeling guitar amps.So if the only number you have left to work with is a "5" for example that means the speaker could have been made in 1955 or 1965.Starting in 1970 they began using TWO digits for the year so it is way easy. However Fender models and cosmetics changed significantly between the 50's and 60's so sorting that out is fairly easy.You'd have to judge from the cosmetics and other design features like handles to decide which decade it was made.If the speaker dates to 1965 that just means the cab could not be an OLDER model than that.