I can confirm the model name Eldorado and 1958...

This watch had been introduced in 1957 and was part of the campaign "Gruen - The Newest Look in Time", which started Christmas 1957 and was intended to be promote for 12 month. Included were 23 jewel watches, the Continental dn Cosmopoitan serias for men, Baguette, Autowind, Caliente and Royalty series for the ladies. Most with innovative styling like this nice example. I have more about it's history and also some more ads.

Scott,

first of all I have to correct myself, the campaign " Gruen - The Newest Look in Time" itself was started 2 years earlier already, prepared already in August for that year's Xmas season. Each year there was a new bunch of models for this campaign. What I meant is that the Eldorado together with some other models were added for the 1957 campaign.
Unfortunately I am right now totally overworked and this state may last until Christmas (hopefully not longer). Until then I fear that I would not be able to afford the hours which are necessary to scan through my archives and get you all I have on the Eldorado. Please post or send me a reminder by PM should I forget about this inquiry during the coming weeks.

Barney