Japan's low-key dollar buying seen in the immediate aftermath of last month's record intervention seems to reflect both a change in tactics in dealing with the yen's strength as well as restraints that make repeated heavy strikes difficult.
The Bank of Japan was spotted selling yen on several occasions in the days that followed the October 31 mammoth $100 billion intervention as the yen resumed its upward creep. The yet unconfirmed action that follows a rare co-ordinated G7 intervention and two potent single-day solo strikes marks a new approach - keeping markets on alert for another big intervention but at a minimal cost.
It may also be a sign that even though Tokyo still has plenty of ammunition, it realises it cannot fire at will because doing so could strain its relations with international partners and have undesired effects at home.
"The only kind of intervention widely acceptable among the G7 is co-ordinated action," a financial source told Reuters.
"Otherwise, there will always be some who will express displeasure."
That means Tokyo may prefer to act as secretly as possible and keep the amount small. Some in the market say the reported timing and scope of the forays suggest that they could be intended as "aftershocks" of the main action meant to help its impact linger longer, rather than part of a lengthy campaign.
Izuru Kato, chief economist at Totan Research in Tokyo, estimates from the BoJ's funds flow data that Japan probably spent 8.7 trillion to 9.1 trillion yen from October 31 to November 4 - just over 8 trillion yen on October 31 and the remainder in the days that followed.
Another financial source agreed, saying that judging from fund flows in the money market, there was a possibility Tokyo may have conducted stealth intervention days after October 31.