* Gold ATMs intended to whet appetite for physical gold

* Private investor inquiries doubling every six weeks

* Plan is for 500 gold ATMs in Germany, Switzerland, Austria

FRANKFURT, May 19 (Reuters) - Private investors should hold up to 15 percent of their wealth in physical gold, according to a German asset management company which plans to set up 500 “Gold-To-Go” ATMs in Germany, Switzerland and Austria this year.

A gold-dispensing automatic teller machine (ATM) was on display at Frankfurt’s main railway station for a one-day marketing test on Tuesday.

A one-gram (0.0353 ounce) piece of gold, the size of a child's little fingernail and about as thin, cost 31 euros ($42.25) -- a 30 percent premium to the spot market price XAU=.

The flat rectangular piece, bearing the imprint of Belgian metals and speciality materials firm Umicore UMI.BR, came out of the cash-only ATM in a tin box, including a certificate of authenticity.

“This is more than a marketing gimmick,” said Thomas Geissler, chief executive of TG-Gold-Super-Markt.de, the company planning to set up the 500 gold ATMs at a cost of 20,000 euros apiece.

“It is an appetizer for a strategic investment in precious metals. Gold is an asset everyone should have, between 5 and 15 percent of your liquid assets in physical gold,” he told Reuters in an interview.

DEMAND

Private investor demand for gold is on the rise in Germany and elsewhere as a result of the financial markets crisis, which has made many investors wary of holding traditional assets such as equities, bonds or mutual funds investing in such securities.

“In absolute numbers, the demand for physical gold is still tiny in Germany,” Geissler said. “But in relative terms, the growth is explosive, inquiries have been doubling every six weeks,” Geissler said of the trend in recent months.

TG-Gold-Super-Mark.de’s main precious metals business idea is based on online commerce.

The gold ATMs to be set up at central locations such as airports, railway stations and shopping malls are intended to gradually accustom people to the idea of investing in physical gold, Geissler said.

The ATMs will dispense 1-gram, 5-gram and 10-gram pieces of gold as well as Krugerrand gold coins. Each ATM can hold up to 1,500 pieces, he said.

The company’s internet website (www.gold-super-mark.de), through which investors can purchase units between 1 gram and 1,000 grams, is updating precious metals prices every 10 minuntes.

The ATMs will be equipped with technology ensuring that the prices charged by the ATMs keep pace with those on the website.

TG-Gold-Super-Markt.de is a subsidiary of German online investment fund company INFOS GmbH founded in 1994. INFOS now manages 170 million euros worth of assets on behalf of about 5,000 customers.