Need info on the history of steel strings, amps in jazz

[Aaron Allen]

Hey All,
Im writing a paper for school about ways in which technology has affected the way the double bass is played in jazz and could use some help. two of the subjects Im discussing are string construction and use of amplification. I need to know when exactly steel strings came onto the market (i think it was some time during the 50's but a more specific date is what im after) and any info about how jazz players at this time responded to them: did many switch to all steel right away or was it more typical to have steel on the bottom strings but keep the gut on top? Regarding amplification, I know that early players such as Blanton played totally acoustic but what about bassists in the 40's, 50's, and 60's? Was their stage volume acoustic but then they played into a mic that went into some speakers out front or ...? Any help on this would be greatly appreciated!
-Aaron