Martin Grelle, Apsaalooke Sentinels, oil, 42 x 48. Estimate: $150,000-$250,000. ← Previous Next → Martin Grelle, Apsaalooke Sentinels, oil, 42 x 48. Estimate: $150,000-$250,000. Martin Grelle, Apsaalooke Sentinels, oil, 42 x 48. Estimate: $150,000-$250,000.