Lockheed C-130B Hercules, N117TG c/n 3018.
IAR moved to Coolidge,AZ with DC8Fs, out of airtanker industry.
And indeed, this Herc looks operational but has no airtanker identification number. It used to carry '31'.

The day of my visit was a sunday and the offices were abandoned, no one around whom I could ask any questions.

Here is the history from Lars Olausson's Hercules Production List:
USAF units: Jul57 61TCS - 1962 18TCS - Aug64 314TCW - May67 4442 CCTW - Nov69 433 TAW ER. To S.Vietnam AF Nov71 and returned to USAF - 327TAS Jan76, Jul76 - Oct77 143 TAS - Dec79, 1981 105 TAS - Apr81, Jan88, last C-130 modified from 'Roman nose', Jun89.
Reg'd N117TG to T&G Aviation, Oct89 (Apr90 white top, Mar91 first civilan aircraft to arrive in Kuwait), Jun92 converted to waterbomber, Jun93 to Securit Civilé France ('81'), participated in test for passive noise suppression, Feb99 leased to RE/Max Ballooning Company, Mar2000 stored at Chandler, Jun02 reg'd to Int'l Air Response, Sep02 operating for the Spanish governement...
[Lockheed Hercules Production List 1954 - 2004, by Lars Olausson]

International Air Response was previously named T & G Aviation.
The company started aerial firefighting operations using 2 leased Douglas DC-7B's. These 'borate bombers' were leased from Arizona-based Airtankers Inc. in 1975. N51701 and N4887C were contracted by the US Forest Service and became based at Wenatchee,WA.
T & G stood for the names of the 2 founders: Sergio Tomassoni and William 'Woody' Grantham. Initially, the company was formed at Buckeye,AZ.
A few years after T&G's formation, a 50 percent share in Airtankers Inc. was bought and in 1979 followed a complete takeover. During 1978 T&G had moved to Chandler Memorial Airport, on the Gila River indian Reservation.
For a long time the Douglas DC-7 was its main type of aircraft and it is great to see N4887C still present here in obvious splendid condition. Bob Wofforth, former Air America pilot, was chief pilot in the early days and also flew N4887C.
Around the early-1980s T&G received a permit to operate adhoc cargo contracts, which included the fish-hauling contracts in Alaska.
The above details were learned from a 1981 copy of Propliner magazine (Vol.11), article written by Stephen Piercey.

Aad van der Voet added: "T&G was formed in 1973, and operated out of Chandler-Memorial Airport. In 1997 they were reorganised as International Air Response Inc. and moved to Coolidge,AZ a short time later. No connection to Gene Packard's former Air Response at Mesa's Falcon Field."

These days, I was told, IAR manages to keep itself in business by "..mostly military suppport ops, para training and even some missile testing."

What a fantastic building!

Airport History:
The Coolidge Municipal Airport was originally constructed in the early 1940’s by the U.S. Dept of the Army.  Originally constructed as an air transport command base, Coolidge Army Airfield served as an auxiliary operating base for Williams Field during WWII. 
The original airfield was constructed with 3 runways in a triangular configuration.
Of these 3 runways, two remain: Runway 17-35 and Runway 5-23. 
Numerous support facilities were constructed, of which a 120-foot by 80-foot hangar still remains.  On 19Jan1950 the airfield was transferred to Pinal County since the airfield was no longer needed by the U.S. Dept of the Army.  Pinal County owned and operated the airport until 1959 when the City of Coolidge obtained ownership of the airport. 
On 02Mar59 the airport was officially transferred from Pinal County ownership to the City of Coolidge.
[Source: http://www.coolidgeaz.com]
The Council intended to tear it down, put up another Wal Mart or something, but I was informaed late Jan.2010: =COOLIDGE WILL KEEP HANGAR!=
'he city council voted last Monday night 25th and was unanimous in repairing the damage to the hangar and continue to maintain and support the hangar as a treasure for all of Arizona...'

See also www.airnav.com/airport/P08

Lockheed C-130A N138FF (c/n 3227) was supposed to be reregistered to N119TG on 05Nov07, but this hasn't been applied. So this aircraft has no operational status for the company, I suppose.

57-0520 (c/n 182-3227) RC-130A was degraded to C-130A in 1969. To Hemet Valley Flying Service as N138FF in 1998 for use as water bomber/chemical spray aircraft. [Source: Joe Baugher]

C-130A N131FF (c/n 3138, ex/ 56-0530 USAF) carried airtanker identification '81' also for Aero Firefighting of which I don't know much, except it was listed as having its headquarters at Anaheim,CA though Tanker 81 seems to have lived mostly at Chandler,AZ.

Nathan Addison wrote me in July 2009:
"I was delighted to see the Hemet-Valley Flying Service C-130s I grew up around as a kid on your website.
They, Hemet-Valley Flying Service, obtained five C-130A aircraft from the US Government to use as air tankers in 1988; they were quickly converted and began use, with two flying in 1989. All were based at Hemet with N138FF and N131FF among them. They were Tanker 81, 82, 83 and 88.
Of those four, all were painted with the exeption of 83, which was quickly prepped for use and was never completely painted to match the others. Instead, Tanker 83 flew in its original olive drab USAF colours with a large orange stripe on the tail that had 83 in the center, and '83' painted just below and behind the cockpit.
A fifth was cannibalized for parts and was only recently removed from Hemet-Ryan in 2008 after sitting there for over a decade.
Tanker 82 (N135FF) was tragically lost in a mid-air explosion and wing seperation in August 1994. An eerie event, foreshadowing of what would happen to the Hawkins & Powers C-130 eight years later...
I think a lot of the registration confusion on some of the aircraft were that they were re-registered to a leasing company after they were obtained... probably the Anaheim hit you got. The strange thing is registration was handed off several times as far as I can tell, but they always remained in the hands of Hemet-Valley Flying Service."

The Road Goes On... back to US Southwest 2008