With its latest funding round, Coinbase, the cryptocurrency exchange turned Silicon Valley unicorn, is amassing a "war chest" for a "rainy day."

At least, that's how Coinbase's vice president of corporate and business development, Emilie Choi, described the $300 million the company recently raised in a Series E round with investors such as Tiger Global Management and Polychain, the latter of which is headed by former Coinbase employee Olaf Carlson-Wee.

"It was opportunistic," Choi told CoinDesk Wednesday. "We didn't need to raise it."

Speaking to why a company reportedly generating  $1.3 billion in annual revenue would continue to court venture capitalists, she added:

Namely, the leading opportunity that Choi sees is adding support for new assets across Coinbase platforms, eventually "thousands" of prospective cryptos.

Beyond the Circle-issued stablecoin that Coinbase already supports, USDC, other fiat-pegged assets may also be under consideration.

"With adding assets, stablecoins are a natural extension of that," Choi said. "As we move towards this utility phase of crypto, we recognize that one of the big things holding users back from actually using crypto was the volatility of it. So a stablecoin helps pave the way for crypto to be more usable and more stable."

She added that diverse categories, such as stablecoins or privacy coins, will naturally emerge as Coinbase adds support for more assets. The company is already considering the privacy-centric asset zcash.

When asked if Coinbase might someday list initial coin offerings (ICOs), tokens launched to fundraise for blockchain projects, Choi replied the company didn't want to "close the door" to any opportunity down the road.

"All the priorities right now are focused on adding assets, adding international rails, all that kind of stuff." she said.

Crypto veteran Arianna Simpson, founder and managing director of Autonomous Partners, described this raise as unusual, but not surprising.

"Usually, when a company of this size raises, it's because they aren't profitable," Simpson told CoinDesk, suggesting the extra funds could bolster the company's global expansion. "[Coinbase] saw the opportunity to raise on favorable terms and they took it."

The exact total raised in this Series E is yet to be released; a second batch of investors is still processing paperwork and endowments.

"This was the first tranche of the primary, we still have a few remaining investors who will do the second tranche," Choi said. But "that [$300 million] will be the bulk of this round."

Venture capitalist Lasse Clausen, co-founder of the Berlin-based fund 1kx, told CoinDesk this raise was particularly impressive since Coinbase reportedly experienced a dramatic drop in active users over the last two quarters. Overall, the research firm Diar found Coinbase's dollar volumes fell 80 percent since last year.

"The revenue and active users of Coinbase have been tanking since December 2017," Clausen said. "So the fact that the investors still deployed this large investment now shows how bullish they are on crypto in the medium and long-term."

That's why Choi said Coinbase is raising now and playing "the long game." The proceeds will also help fund international expansion, she said.

"Certainly the U.K. has been a big focus for us. We'll probably have more expansion and extension in the EU more broadly," Choi said. "We're definitely very bullish on Japan as the first Asian market that we really want to enter."

Indeed, Coinbase is hiring for several roles in the new London and Tokyo offices. As such, Choi said the Series E, which valued the company at a record $8 billion, will help it make competitive employment offers.

Speaking to Coinbase's aim to eventually raise funds through an initial public offering as well, albeit not any time soon, Choi added:

Emilie Choi image via Coinbase