This morning, IndexUniverse.com managing editor Olly Ludwig asked if the JPMorgan Alerian MLP ETN (NYSEArca: AMJ) would start trading at a premium after JPMorgan capped the note's shares.

Guess what? It is. At least, a tiny one.

At market close on Friday, AMJ was trading at a 0.19 percent premium to its indicative value. “It's essentially a free gift,” said Chris Hempstead of WallachBeth Captial, speaking with Barrons.com on the matter.

It makes sense. After all, when creations of new shares are halted, high demand for shares  will push the price higher. The question all of the note's investors will ask themselves over the weekend, however, is whether the premium will continue.

Imagine a scenario in which JP Morgan decides to reopen the ETN to new shares. The bank hasn't indicated that will happen, but it's bound to happen at some point. When the ETN reopens, the current premiums will pop like a bubble, leaving investors holding the bag.

But if shares of AMJ remain capped, that premium will continue to grow. How long do you watch the premium go before selling the shares out?

What makes this trade fascinating is how an investment in AMJ has suddenly changed: You're not just buying exposure to master-limited partnerships, you're now also betting on how other investors will treat the ETN itself.

Two other ETNs recently experienced premiums due to stopped creations. In March, the VelocityShares Daily 2X VIX Short ETN (NYSEArca: TVIX) plunged more than 30 percent after Credit Suisse announced creations would resume. TVIX's premium at the time had reached nearly 100 percent. IU's own Dave Nadig and Matt Hougan questioned whether news of TVIX's reopened creations leaked early.

Another ETN, the iPath Natural Gas ETN (NYSEArca: GAZ) also reached epic premium levels in early April, even though creations had been closed since 2009. The ETN remains at a 41 percent premium as of market close on Friday.