So how can I find out when my Sunn Spectrum I (It's a I not a II)

[stringbender55]

was built? I am thinking it was between Sept. 67 and July 68

It has a serial # of #2397.

That's all. It has a 1 15 cab with an Electro Voice in it.

I just got it and had the pots changed and rebiased and new tubes put in.

It IS LOUD!

I just wondered what it is worth and when it was built?

Thanks,
String Bender55

[EdBass]

AFAIK the serial # isn't any help, but the Spectrum II was only in the '67 and '68 catalog, so your thoughts on vintage are probably pretty close.
Usually old Sunns have an inspection sticker somewhere on the chassis with an inspection date, sometimes they have a date written in grease pencil on the chassis.

As far as it's "worth"; well it's worth nothing unless it's for sale, and if it is for sale it's worth whatever someone will pay you for it. Regretfully eBay is about the only national/international open market barometer of old amp true market worth, precious few old Sunns get sold there relative to other vintage amps; it's a cyclical market and the Sunns that are there fluctuate in price pretty dramatically.
Much to my dismay, it seems the vintage Sunn market is on another down swing. 2000S's are mostly bringing under a grand, and last weekend I was pitched a nice '73 Model T for $1200.
Not long ago nice 2000S's were bringing $1500+, 100S/200S in the $600 range, and this very forum has been buzzing with tales of $2500ish Model T's very recently.
The only thing even close to your Spectrum II I've seen lately is a 100S (w/ reverb, needing some TLC) that went for $405 on 7/31. The 100S is the same amp as the Spectrum II, but likely has much better name recognition because it is associated with some iconic players, most notably Pete Townshend.

So... What would you take for it? 

[stringbender55]

I just got it. I traded an Epiphone PSR 275 SC for it. Then put it in the shop for it to be recapped and retubed. I put it on 1 and the floors and walls shook. I started on a Sunn Sonaro and loved the sounds I got. That was 1969/70 and I like this amp a lot, so I think I will keep it. I am pretty sure the guy I got it from didn't know what it was worth. The guitar was worth many $200-250. So I think I got the better end of the deal by a long shot. I think his brother bought it new in 1967.

It has that Grand Funk LOUD and Big Bass sound. I love it. Thanks for the help.

[stringbender55]

Why don't the serial numbers mean anything?

[EdBass]

Why don't the serial numbers mean anything?

Maybe there is a way to use the Sunn serials, but I sure don't know how. I don't think there is any correlation between the serial numbers and model or year. I've never come across info to decode Sunn serial #'s in searching the internet, but I've never actually asked Mr. Sundholm about that though.
I've noticed that inconsistent serial numbers are the norm with most vintage gear, not just Sunn stuff. Even Fender amps are virtually impossible to accurately date with the serial number, and because of their popularity and the corresponding value of vintage Fender gear there has been considerable effort made by very knowledgeable collectors/authors to decode them.
Also, Mark Huss is probably the most knowledgeable vintage Hiwatt expert on earth, and his extensive and exhaustive research into Hiwatt has only narrowed them down to "approximate" year of manufacture.
 

By the way, regardless of whatever the "actual cash value" of your amp may be, for what it's worth I would personally be ticked pink to have got the deal you got on your Spectrum II! 

[stringbender55]

I assume a Spectrum I has 1 15 and a Spectrum has 2 15's in the cab?

Or is the 1 the first model and the 2 a second model?

[EdBass]

I assume a Spectrum I has 1 15 and a Spectrum has 2 15's in the cab?

Or is the 1 the first model and the 2 a second model?

The Spectrum I is a 40 watt 2 X EL34 amp and the Spectrum II is a 60 watt 2 X KT88 amp. The Spectrum II came with a 2 X JBL D15S/D130 cab, and I ASSUME the Spectrum I came with a single JBL D15S/D130, as was the case with other Sunn EL34 amps, but I've never actually seen one.